diff --git a/src/include/86box/vid_cga.h b/src/include/86box/vid_cga.h
index a84373d84..7f68286e5 100644
--- a/src/include/86box/vid_cga.h
+++ b/src/include/86box/vid_cga.h
@@ -56,6 +56,7 @@ typedef enum cga_crtc_registers_e
     CGA_CRTC_LIGHT_PEN_ADDR_LOW = 0x11,                 // Light pen address low 8 bits (not currently supported)
 } cga_crtc_registers;
 
+// Registers for the CGA
 typedef enum cga_registers_e
 {
     CGA_REGISTER_CRTC_INDEX = 0x3D4,
diff --git a/src/machine/m_amstrad.c b/src/machine/m_amstrad.c
index b57eac60d..af6c50bc9 100644
--- a/src/machine/m_amstrad.c
+++ b/src/machine/m_amstrad.c
@@ -369,26 +369,26 @@ vid_poll_1512(void *priv)
             for (c = 0; c < 8; c++) {
                 if ((vid->cgamode & 0x12) == 0x12) {
                     buffer32->line[vid->displine << 1][c] = buffer32->line[(vid->displine << 1) + 1][c] = (vid->border & 15) + 16;
-                    if (vid->cgamode & 1) {
+                    if (vid->cgamode & CGA_MODE_FLAG_HIGHRES) {
                         buffer32->line[vid->displine << 1][c + (vid->crtc[1] << 3) + 8] = buffer32->line[(vid->displine << 1) + 1][c + (vid->crtc[1] << 3) + 8] = 0;
                     } else {
                         buffer32->line[vid->displine << 1][c + (vid->crtc[1] << 4) + 8] = buffer32->line[(vid->displine << 1) + 1][c + (vid->crtc[1] << 4) + 8] = 0;
                     }
                 } else {
                     buffer32->line[vid->displine << 1][c] = buffer32->line[(vid->displine << 1) + 1][c] = (vid->cgacol & 15) + 16;
-                    if (vid->cgamode & 1) {
+                    if (vid->cgamode & CGA_MODE_FLAG_HIGHRES) {
                         buffer32->line[vid->displine << 1][c + (vid->crtc[1] << 3) + 8] = buffer32->line[(vid->displine << 1) + 1][c + (vid->crtc[1] << 3) + 8] = (vid->cgacol & 15) + 16;
                     } else {
                         buffer32->line[vid->displine << 1][c + (vid->crtc[1] << 4) + 8] = buffer32->line[(vid->displine << 1) + 1][c + (vid->crtc[1] << 4) + 8] = (vid->cgacol & 15) + 16;
                     }
                 }
             }
-            if (vid->cgamode & 1) {
+            if (vid->cgamode & CGA_MODE_FLAG_HIGHRES) {
                 for (x = 0; x < 80; x++) {
                     chr        = vid->vram[(vid->ma << 1) & 0x3fff];
                     attr       = vid->vram[((vid->ma << 1) + 1) & 0x3fff];
                     drawcursor = ((vid->ma == ca) && vid->con && vid->cursoron);
-                    if (vid->cgamode & 0x20) {
+                    if (vid->cgamode & CGA_MODE_FLAG_BLINK) {
                         cols[1] = (attr & 15) + 16;
                         cols[0] = ((attr >> 4) & 7) + 16;
                         if ((vid->blink & 16) && (attr & 0x80) && !drawcursor)
@@ -408,12 +408,12 @@ vid_poll_1512(void *priv)
                     }
                     vid->ma++;
                 }
-            } else if (!(vid->cgamode & 2)) {
+            } else if (!(vid->cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                 for (x = 0; x < 40; x++) {
                     chr        = vid->vram[(vid->ma << 1) & 0x3fff];
                     attr       = vid->vram[((vid->ma << 1) + 1) & 0x3fff];
                     drawcursor = ((vid->ma == ca) && vid->con && vid->cursoron);
-                    if (vid->cgamode & 0x20) {
+                    if (vid->cgamode & CGA_MODE_FLAG_BLINK) {
                         cols[1] = (attr & 15) + 16;
                         cols[0] = ((attr >> 4) & 7) + 16;
                         if ((vid->blink & 16) && (attr & 0x80))
@@ -433,10 +433,10 @@ vid_poll_1512(void *priv)
                         }
                     }
                 }
-            } else if (!(vid->cgamode & 16)) {
+            } else if (!(vid->cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)) {
                 cols[0] = (vid->cgacol & 15) | 16;
                 col     = (vid->cgacol & 16) ? 24 : 16;
-                if (vid->cgamode & 4) {
+                if (vid->cgamode & CGA_MODE_FLAG_BW) {
                     cols[1] = col | 3;
                     cols[2] = col | 4;
                     cols[3] = col | 7;
@@ -477,7 +477,7 @@ vid_poll_1512(void *priv)
             }
         } else {
             cols[0] = ((vid->cgamode & 0x12) == 0x12) ? 0 : (vid->cgacol & 15) + 16;
-            if (vid->cgamode & 1) {
+            if (vid->cgamode & CGA_MODE_FLAG_HIGHRES) {
                 hline(buffer32, 0, (vid->displine << 1), (vid->crtc[1] << 3) + 16, cols[0]);
                 hline(buffer32, 0, (vid->displine << 1) + 1, (vid->crtc[1] << 3) + 16, cols[0]);
             } else {
@@ -486,7 +486,7 @@ vid_poll_1512(void *priv)
             }
         }
 
-        if (vid->cgamode & 1)
+        if (vid->cgamode & CGA_MODE_FLAG_HIGHRES)
             x = (vid->crtc[1] << 3) + 16;
         else
             x = (vid->crtc[1] << 4) + 16;
@@ -545,7 +545,7 @@ vid_poll_1512(void *priv)
                 vid->displine  = 0;
                 vid->vsynctime = 46;
 
-                if (vid->cgamode & 1)
+                if (vid->cgamode & CGA_MODE_FLAG_HIGHRES)
                     x = (vid->crtc[1] << 3) + 16;
                 else
                     x = (vid->crtc[1] << 4) + 16;
@@ -582,15 +582,15 @@ vid_poll_1512(void *priv)
 
                 video_res_x = xsize;
                 video_res_y = ysize;
-                if (vid->cgamode & 1) {
+                if (vid->cgamode & CGA_MODE_FLAG_HIGHRES) {
                     video_res_x /= 8;
                     video_res_y /= vid->crtc[9] + 1;
                     video_bpp = 0;
-                } else if (!(vid->cgamode & 2)) {
+                } else if (!(vid->cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                     video_res_x /= 16;
                     video_res_y /= vid->crtc[9] + 1;
                     video_bpp = 0;
-                } else if (!(vid->cgamode & 16)) {
+                } else if (!(vid->cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)) {
                     video_res_x /= 2;
                     video_bpp = 2;
                 } else {
@@ -1403,14 +1403,14 @@ lcdc_poll(amsvid_t *vid)
     uint16_t ca;
     int      blink;
 
-    ca = (cga->crtc[15] | (cga->crtc[14] << 8)) & 0x3fff;
+    ca = (cga->crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (cga->crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x3fff;
 
     if (!cga->linepos) {
         timer_advance_u64(&vid->timer, cga->dispofftime);
         cga->cgastat |= 1;
         cga->linepos = 1;
         oldsc        = cga->sc;
-        if ((cga->crtc[8] & 3) == 3)
+        if ((cga->crtc[CGA_CRTC_INTERLACE] & 3) == 3)
             cga->sc = ((cga->sc << 1) + cga->oddeven) & 7;
         if (cga->cgadispon) {
             if (cga->displine < cga->firstline) {
@@ -1419,28 +1419,28 @@ lcdc_poll(amsvid_t *vid)
             }
             cga->lastline = cga->displine;
 
-            if (cga->cgamode & 1) {
-                for (x = 0; x < cga->crtc[1]; x++) {
+            if (cga->cgamode & CGA_MODE_FLAG_HIGHRES) {
+                for (x = 0; x < cga->crtc[CGA_CRTC_HDISP]; x++) {
                     chr        = cga->charbuffer[x << 1];
                     attr       = cga->charbuffer[(x << 1) + 1];
                     drawcursor = ((cga->ma == ca) && cga->cursorvisible && cga->cursoron);
-                    blink      = ((cga->cgablink & 16) && (cga->cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+                    blink      = ((cga->cgablink & 16) && (cga->cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
                     lcd_draw_char_80(vid, &(buffer32->line[cga->displine << 1])[x * 8], chr, attr, drawcursor, blink, cga->sc, cga->cgamode & 0x40, cga->cgamode);
                     lcd_draw_char_80(vid, &(buffer32->line[(cga->displine << 1) + 1])[x * 8], chr, attr, drawcursor, blink, cga->sc, cga->cgamode & 0x40, cga->cgamode);
                     cga->ma++;
                 }
-            } else if (!(cga->cgamode & 2)) {
-                for (x = 0; x < cga->crtc[1]; x++) {
+            } else if (!(cga->cgamode & CGA_MODE_FLAG_GRAPHICS)) {
+                for (x = 0; x < cga->crtc[CGA_CRTC_HDISP]; x++) {
                     chr        = cga->vram[(cga->ma << 1) & 0x3fff];
                     attr       = cga->vram[((cga->ma << 1) + 1) & 0x3fff];
                     drawcursor = ((cga->ma == ca) && cga->cursorvisible && cga->cursoron);
-                    blink      = ((cga->cgablink & 16) && (cga->cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+                    blink      = ((cga->cgablink & 16) && (cga->cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
                     lcd_draw_char_40(vid, &(buffer32->line[cga->displine << 1])[x * 16], chr, attr, drawcursor, blink, cga->sc, cga->cgamode);
                     lcd_draw_char_40(vid, &(buffer32->line[(cga->displine << 1) + 1])[x * 16], chr, attr, drawcursor, blink, cga->sc, cga->cgamode);
                     cga->ma++;
                 }
             } else { /* Graphics mode */
-                for (x = 0; x < cga->crtc[1]; x++) {
+                for (x = 0; x < cga->crtc[CGA_CRTC_HDISP]; x++) {
                     dat = (cga->vram[((cga->ma << 1) & 0x1fff) + ((cga->sc & 1) * 0x2000)] << 8) | cga->vram[((cga->ma << 1) & 0x1fff) + ((cga->sc & 1) * 0x2000) + 1];
                     cga->ma++;
                     for (uint8_t c = 0; c < 16; c++) {
@@ -1450,22 +1450,22 @@ lcdc_poll(amsvid_t *vid)
                 }
             }
         } else {
-            if (cga->cgamode & 1) {
-                hline(buffer32, 0, (cga->displine << 1), (cga->crtc[1] << 3), green);
-                hline(buffer32, 0, (cga->displine << 1) + 1, (cga->crtc[1] << 3), green);
+            if (cga->cgamode & CGA_MODE_FLAG_HIGHRES) {
+                hline(buffer32, 0, (cga->displine << 1), (cga->crtc[CGA_CRTC_HDISP] << 3), green);
+                hline(buffer32, 0, (cga->displine << 1) + 1, (cga->crtc[CGA_CRTC_HDISP] << 3), green);
             } else {
-                hline(buffer32, 0, (cga->displine << 1), (cga->crtc[1] << 4), green);
-                hline(buffer32, 0, (cga->displine << 1) + 1, (cga->crtc[1] << 4), green);
+                hline(buffer32, 0, (cga->displine << 1), (cga->crtc[CGA_CRTC_HDISP] << 4), green);
+                hline(buffer32, 0, (cga->displine << 1) + 1, (cga->crtc[CGA_CRTC_HDISP] << 4), green);
             }
         }
 
-        if (cga->cgamode & 1)
-            x = (cga->crtc[1] << 3);
+        if (cga->cgamode & CGA_MODE_FLAG_HIGHRES)
+            x = (cga->crtc[CGA_CRTC_HDISP] << 3);
         else
-            x = (cga->crtc[1] << 4);
+            x = (cga->crtc[CGA_CRTC_HDISP] << 4);
 
         cga->sc = oldsc;
-        if (cga->vc == cga->crtc[7] && !cga->sc)
+        if (cga->vc == cga->crtc[CGA_CRTC_VSYNC] && !cga->sc)
             cga->cgastat |= 8;
         cga->displine++;
         if (cga->displine >= 360)
@@ -1478,10 +1478,10 @@ lcdc_poll(amsvid_t *vid)
             if (!cga->vsynctime)
                 cga->cgastat &= ~8;
         }
-        if (cga->sc == (cga->crtc[11] & 31) || ((cga->crtc[8] & 3) == 3 && cga->sc == ((cga->crtc[11] & 31) >> 1))) {
+        if (cga->sc == (cga->crtc[CGA_CRTC_CURSOR_END] & 31) || ((cga->crtc[CGA_CRTC_INTERLACE] & 3) == 3 && cga->sc == ((cga->crtc[CGA_CRTC_CURSOR_END] & 31) >> 1))) {
             cga->cursorvisible  = 0;
         }
-        if ((cga->crtc[8] & 3) == 3 && cga->sc == (cga->crtc[9] >> 1))
+        if ((cga->crtc[CGA_CRTC_INTERLACE] & 3) == 3 && cga->sc == (cga->crtc[CGA_CRTC_MAX_SCANLINE_ADDR] >> 1))
             cga->maback = cga->ma;
         if (cga->vadj) {
             cga->sc++;
@@ -1490,41 +1490,41 @@ lcdc_poll(amsvid_t *vid)
             cga->vadj--;
             if (!cga->vadj) {
                 cga->cgadispon = 1;
-                cga->ma = cga->maback = (cga->crtc[13] | (cga->crtc[12] << 8)) & 0x3fff;
+                cga->ma = cga->maback = (cga->crtc[CGA_CRTC_START_ADDR_LOW] | (cga->crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
                 cga->sc               = 0;
             }
-        } else if (cga->sc == cga->crtc[9]) {
+        } else if (cga->sc == cga->crtc[CGA_CRTC_MAX_SCANLINE_ADDR]) {
             cga->maback = cga->ma;
             cga->sc     = 0;
             oldvc       = cga->vc;
             cga->vc++;
             cga->vc &= 127;
 
-            if (cga->vc == cga->crtc[6])
+            if (cga->vc == cga->crtc[CGA_CRTC_VDISP])
                 cga->cgadispon = 0;
 
-            if (oldvc == cga->crtc[4]) {
+            if (oldvc == cga->crtc[CGA_CRTC_VTOTAL]) {
                 cga->vc   = 0;
-                cga->vadj = cga->crtc[5];
+                cga->vadj = cga->crtc[CGA_CRTC_VTOTAL_ADJUST];
                 if (!cga->vadj)
                     cga->cgadispon = 1;
                 if (!cga->vadj)
-                    cga->ma = cga->maback = (cga->crtc[13] | (cga->crtc[12] << 8)) & 0x3fff;
-                if ((cga->crtc[10] & 0x60) == 0x20)
+                    cga->ma = cga->maback = (cga->crtc[CGA_CRTC_START_ADDR_LOW] | (cga->crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
+                if ((cga->crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20)
                     cga->cursoron = 0;
                 else
                     cga->cursoron = cga->cgablink & 8;
             }
 
-            if (cga->vc == cga->crtc[7]) {
+            if (cga->vc == cga->crtc[CGA_CRTC_VSYNC]) {
                 cga->cgadispon = 0;
                 cga->displine  = 0;
                 cga->vsynctime = 16;
-                if (cga->crtc[7]) {
-                    if (cga->cgamode & 1)
-                        x = (cga->crtc[1] << 3);
+                if (cga->crtc[CGA_CRTC_VSYNC]) {
+                    if (cga->cgamode & CGA_MODE_FLAG_HIGHRES)
+                        x = (cga->crtc[CGA_CRTC_HDISP] << 3);
                     else
-                        x = (cga->crtc[1] << 4);
+                        x = (cga->crtc[CGA_CRTC_HDISP] << 4);
                     cga->lastline++;
 
                     xs_temp = x;
@@ -1536,7 +1536,7 @@ lcdc_poll(amsvid_t *vid)
                         if (ys_temp < 32)
                             ys_temp = 400;
 
-                        if ((cga->cgamode & 8) && ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get())) {
+                        if ((cga->cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get())) {
                             xsize = xs_temp;
                             ysize = ys_temp;
                             set_screen_size(xsize, ysize);
@@ -1553,15 +1553,15 @@ lcdc_poll(amsvid_t *vid)
 
                     video_res_x = xsize;
                     video_res_y = ysize;
-                    if (cga->cgamode & 1) {
+                    if (cga->cgamode & CGA_MODE_FLAG_HIGHRES) {
                         video_res_x /= 8;
-                        video_res_y /= cga->crtc[9] + 1;
+                        video_res_y /= cga->crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1;
                         video_bpp = 0;
-                    } else if (!(cga->cgamode & 2)) {
+                    } else if (!(cga->cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                         video_res_x /= 16;
-                        video_res_y /= cga->crtc[9] + 1;
+                        video_res_y /= cga->crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1;
                         video_bpp = 0;
-                    } else if (!(cga->cgamode & 16)) {
+                    } else if (!(cga->cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)) {
                         video_res_x /= 2;
                         video_bpp = 2;
                     } else
@@ -1579,10 +1579,10 @@ lcdc_poll(amsvid_t *vid)
         }
         if (cga->cgadispon)
             cga->cgastat &= ~1;
-        if (cga->sc == (cga->crtc[10] & 31) || ((cga->crtc[8] & 3) == 3 && cga->sc == ((cga->crtc[10] & 31) >> 1)))
+        if (cga->sc == (cga->crtc[CGA_CRTC_CURSOR_START] & 31) || ((cga->crtc[CGA_CRTC_INTERLACE] & 3) == 3 && cga->sc == ((cga->crtc[CGA_CRTC_CURSOR_START] & 31) >> 1)))
             cga->cursorvisible = 1;
-        if (cga->cgadispon && (cga->cgamode & 1)) {
-            for (x = 0; x < (cga->crtc[1] << 1); x++)
+        if (cga->cgadispon && (cga->cgamode & CGA_MODE_FLAG_HIGHRES)) {
+            for (x = 0; x < (cga->crtc[CGA_CRTC_HDISP] << 1); x++)
                 cga->charbuffer[x] = cga->vram[((cga->ma << 1) + x) & 0x3fff];
         }
     }
diff --git a/src/machine/m_at_compaq.c b/src/machine/m_at_compaq.c
index 1f5ecdb58..aaa22ffc0 100644
--- a/src/machine/m_at_compaq.c
+++ b/src/machine/m_at_compaq.c
@@ -276,8 +276,8 @@ compaq_plasma_poll(void *priv)
     uint8_t  chr;
     uint8_t  attr;
     uint8_t  sc;
-    uint16_t ma  = (self->cga.crtc[13] | (self->cga.crtc[12] << 8)) & 0x7fff;
-    uint16_t ca  = (self->cga.crtc[15] | (self->cga.crtc[14] << 8)) & 0x7fff;
+    uint16_t ma  = (self->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (self->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x7fff;
+    uint16_t ca  = (self->cga.crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (self->cga.crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x7fff;
     uint16_t addr;
     int      drawcursor;
     int      cursorline;
@@ -321,10 +321,10 @@ compaq_plasma_poll(void *priv)
                     addr = ((ma & ~1) + (self->cga.displine >> 4) * 80) << 1;
                     ma += (self->cga.displine >> 4) * 80;
 
-                    if ((self->cga.crtc[0x0a] & 0x60) == 0x20)
+                    if ((self->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20)
                         cursorline = 0;
                     else
-                        cursorline = (((self->cga.crtc[0x0a] & 0x0f) << 1) <= sc) && (((self->cga.crtc[0x0b] & 0x0f) << 1) >= sc);
+                        cursorline = (((self->cga.crtc[CGA_CRTC_CURSOR_START] & 0x0f) << 1) <= sc) && (((self->cga.crtc[CGA_CRTC_CURSOR_END] & 0x0f) << 1) >= sc);
 
                     /* for each text column */
                     for (x = 0; x < 80; x++) {
@@ -352,7 +352,7 @@ compaq_plasma_poll(void *priv)
                         /* set foreground */
                         cols[1] = blinkcols[attr][1];
                         /* blink active */
-                        if (self->cga.cgamode & 0x20) {
+                        if (self->cga.cgamode & CGA_MODE_FLAG_BLINK) {
                             cols[0] = blinkcols[attr][0];
                             /* attribute 7 active and not cursor */
                             if ((self->cga.cgablink & 0x08) && (attr & 0x80) && !drawcursor) {
@@ -406,10 +406,10 @@ compaq_plasma_poll(void *priv)
                     addr = ((ma & ~1) + (self->cga.displine >> 4) * 40) << 1;
                     ma += (self->cga.displine >> 4) * 40;
 
-                    if ((self->cga.crtc[0x0a] & 0x60) == 0x20)
+                    if ((self->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20)
                         cursorline = 0;
                     else
-                        cursorline = (((self->cga.crtc[0x0a] & 0x0f) << 1) <= sc) && (((self->cga.crtc[0x0b] & 0x0f) << 1) >= sc);
+                        cursorline = (((self->cga.crtc[CGA_CRTC_CURSOR_START] & 0x0f) << 1) <= sc) && (((self->cga.crtc[CGA_CRTC_CURSOR_END] & 0x0f) << 1) >= sc);
 
                     for (x = 0; x < 40; x++) {
                         /* video output enabled */
@@ -436,7 +436,7 @@ compaq_plasma_poll(void *priv)
                         /* set foreground */
                         cols[1] = blinkcols[attr][1];
                         /* blink active */
-                        if (self->cga.cgamode & 0x20) {
+                        if (self->cga.cgamode & CGA_MODE_FLAG_BLINK) {
                             cols[0] = blinkcols[attr][0];
                             /* attribute 7 active and not cursor */
                             if ((self->cga.cgablink & 0x08) && (attr & 0x80) && !drawcursor) {
@@ -485,7 +485,7 @@ compaq_plasma_poll(void *priv)
                         ma++;
                     }
                 } else {
-                    if (self->cga.cgamode & 0x10) {
+                    if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS) {
                         /* 640x400 mode */
                         if (self->port_23c6 & 0x01) /* 640*400 */ {
                             addr = ((self->cga.displine) & 1) * 0x2000 + ((self->cga.displine >> 1) & 1) * 0x4000 + (self->cga.displine >> 2) * 80 + ((ma & ~1) << 1);
@@ -589,7 +589,7 @@ compaq_plasma_poll(void *priv)
                 video_res_y = 400;
 
                 if (self->cga.cgamode & 0x02) {
-                    if (self->cga.cgamode & 0x10)
+                    if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)
                         video_bpp = 1;
                     else
                         video_bpp = 2;
diff --git a/src/machine/m_at_t3100e_vid.c b/src/machine/m_at_t3100e_vid.c
index c827a05e5..0346fccd4 100644
--- a/src/machine/m_at_t3100e_vid.c
+++ b/src/machine/m_at_t3100e_vid.c
@@ -255,24 +255,24 @@ t3100e_text_row80(t3100e_t *t3100e)
     int      blink;
     uint16_t addr;
     uint8_t  sc;
-    uint16_t ma = (t3100e->cga.crtc[13] | (t3100e->cga.crtc[12] << 8)) & 0x7fff;
-    uint16_t ca = (t3100e->cga.crtc[15] | (t3100e->cga.crtc[14] << 8)) & 0x7fff;
+    uint16_t ma = (t3100e->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (t3100e->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x7fff;
+    uint16_t ca = (t3100e->cga.crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (t3100e->cga.crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x7fff;
 
     sc   = (t3100e->displine) & 15;
     addr = ((ma & ~1) + (t3100e->displine >> 4) * 80) * 2;
     ma += (t3100e->displine >> 4) * 80;
 
-    if ((t3100e->cga.crtc[10] & 0x60) == 0x20) {
+    if ((t3100e->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20) {
         cursorline = 0;
     } else {
-        cursorline = ((t3100e->cga.crtc[10] & 0x0F) * 2 <= sc) && ((t3100e->cga.crtc[11] & 0x0F) * 2 >= sc);
+        cursorline = ((t3100e->cga.crtc[CGA_CRTC_CURSOR_START] & 0x0F) * 2 <= sc) && ((t3100e->cga.crtc[CGA_CRTC_CURSOR_END] & 0x0F) * 2 >= sc);
     }
     for (uint8_t x = 0; x < 80; x++) {
         chr        = t3100e->vram[(addr + 2 * x) & 0x7FFF];
         attr       = t3100e->vram[(addr + 2 * x + 1) & 0x7FFF];
-        drawcursor = ((ma == ca) && cursorline && (t3100e->cga.cgamode & 8) && (t3100e->cga.cgablink & 16));
+        drawcursor = ((ma == ca) && cursorline && (t3100e->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && (t3100e->cga.cgablink & 16));
 
-        blink = ((t3100e->cga.cgablink & 16) && (t3100e->cga.cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+        blink = ((t3100e->cga.cgablink & 16) && (t3100e->cga.cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
 
         if (t3100e->video_options & 4)
             bold = boldcols[attr] ? chr + 256 : chr;
@@ -280,7 +280,7 @@ t3100e_text_row80(t3100e_t *t3100e)
             bold = boldcols[attr] ? chr : chr + 256;
         bold += 512 * (t3100e->video_options & 3);
 
-        if (t3100e->cga.cgamode & 0x20) /* Blink */
+        if (t3100e->cga.cgamode & CGA_MODE_FLAG_BLINK) /* Blink */
         {
             cols[1] = blinkcols[attr][1];
             cols[0] = blinkcols[attr][0];
@@ -316,24 +316,24 @@ t3100e_text_row40(t3100e_t *t3100e)
     int      blink;
     uint16_t addr;
     uint8_t  sc;
-    uint16_t ma = (t3100e->cga.crtc[13] | (t3100e->cga.crtc[12] << 8)) & 0x7fff;
-    uint16_t ca = (t3100e->cga.crtc[15] | (t3100e->cga.crtc[14] << 8)) & 0x7fff;
+    uint16_t ma = (t3100e->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (t3100e->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x7fff;
+    uint16_t ca = (t3100e->cga.crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (t3100e->cga.crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x7fff;
 
     sc   = (t3100e->displine) & 15;
     addr = ((ma & ~1) + (t3100e->displine >> 4) * 40) * 2;
     ma += (t3100e->displine >> 4) * 40;
 
-    if ((t3100e->cga.crtc[10] & 0x60) == 0x20) {
+    if ((t3100e->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20) {
         cursorline = 0;
     } else {
-        cursorline = ((t3100e->cga.crtc[10] & 0x0F) * 2 <= sc) && ((t3100e->cga.crtc[11] & 0x0F) * 2 >= sc);
+        cursorline = ((t3100e->cga.crtc[CGA_CRTC_CURSOR_START] & 0x0F) * 2 <= sc) && ((t3100e->cga.crtc[CGA_CRTC_CURSOR_END] & 0x0F) * 2 >= sc);
     }
     for (uint8_t x = 0; x < 40; x++) {
         chr        = t3100e->vram[(addr + 2 * x) & 0x7FFF];
         attr       = t3100e->vram[(addr + 2 * x + 1) & 0x7FFF];
-        drawcursor = ((ma == ca) && cursorline && (t3100e->cga.cgamode & 8) && (t3100e->cga.cgablink & 16));
+        drawcursor = ((ma == ca) && cursorline && (t3100e->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && (t3100e->cga.cgablink & 16));
 
-        blink = ((t3100e->cga.cgablink & 16) && (t3100e->cga.cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+        blink = ((t3100e->cga.cgablink & 16) && (t3100e->cga.cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
 
         if (t3100e->video_options & 4)
             bold = boldcols[attr] ? chr + 256 : chr;
@@ -341,7 +341,7 @@ t3100e_text_row40(t3100e_t *t3100e)
             bold = boldcols[attr] ? chr : chr + 256;
         bold += 512 * (t3100e->video_options & 3);
 
-        if (t3100e->cga.cgamode & 0x20) /* Blink */
+        if (t3100e->cga.cgamode & CGA_MODE_FLAG_BLINK) /* Blink */
         {
             cols[1] = blinkcols[attr][1];
             cols[0] = blinkcols[attr][0];
@@ -374,9 +374,9 @@ t3100e_cgaline6(t3100e_t *t3100e)
     uint32_t fg = (t3100e->cga.cgacol & 0x0F) ? amber : black;
     uint32_t bg = black;
 
-    uint16_t ma = (t3100e->cga.crtc[13] | (t3100e->cga.crtc[12] << 8)) & 0x7fff;
+    uint16_t ma = (t3100e->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (t3100e->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x7fff;
 
-    if (t3100e->cga.crtc[9] == 3) /* 640*400 */
+    if (t3100e->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] == 3) /* 640*400 */
     {
         addr = ((t3100e->displine) & 1) * 0x2000 + ((t3100e->displine >> 1) & 1) * 0x4000 + (t3100e->displine >> 2) * 80 + ((ma & ~1) << 1);
     } else {
@@ -388,7 +388,7 @@ t3100e_cgaline6(t3100e_t *t3100e)
 
         for (uint8_t c = 0; c < 8; c++) {
             ink = (dat & 0x80) ? fg : bg;
-            if (!(t3100e->cga.cgamode & 8))
+            if (!(t3100e->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE))
                 ink = black;
             (buffer32->line[t3100e->displine])[x * 8 + c] = ink;
             dat                                           = dat << 1;
@@ -407,8 +407,8 @@ t3100e_cgaline4(t3100e_t *t3100e)
     uint32_t ink1 = 0;
     uint16_t addr;
 
-    uint16_t ma = (t3100e->cga.crtc[13] | (t3100e->cga.crtc[12] << 8)) & 0x7fff;
-    if (t3100e->cga.crtc[9] == 3) /* 320*400 undocumented */
+    uint16_t ma = (t3100e->cga.crtc[CGA_CRTC_START_ADDR_HIGH] | (t3100e->cga.crtc[CGA_CRTC_CURSOR_END] << 8)) & 0x7fff;
+    if (t3100e->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] == 3) /* 320*400 undocumented */
     {
         addr = ((t3100e->displine) & 1) * 0x2000 + ((t3100e->displine >> 1) & 1) * 0x4000 + (t3100e->displine >> 2) * 80 + ((ma & ~1) << 1);
     } else /* 320*200 */
@@ -421,7 +421,7 @@ t3100e_cgaline4(t3100e_t *t3100e)
 
         for (uint8_t c = 0; c < 4; c++) {
             pattern = (dat & 0xC0) >> 6;
-            if (!(t3100e->cga.cgamode & 8))
+            if (!(t3100e->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE))
                 pattern = 0;
 
             switch (pattern & 3) {
@@ -498,7 +498,7 @@ t3100e_poll(void *priv)
 
             /* Graphics */
             if (t3100e->cga.cgamode & 0x02) {
-                if (t3100e->cga.cgamode & 0x10)
+                if (t3100e->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)
                     t3100e_cgaline6(t3100e);
                 else
                     t3100e_cgaline4(t3100e);
@@ -551,7 +551,7 @@ t3100e_poll(void *priv)
             video_res_y = T3100E_YSIZE;
 
             if (t3100e->cga.cgamode & 0x02) {
-                if (t3100e->cga.cgamode & 0x10)
+                if (t3100e->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)
                     video_bpp = 1;
                 else
                     video_bpp = 2;
diff --git a/src/machine/m_elt.c b/src/machine/m_elt.c
index 812755898..628333aba 100644
--- a/src/machine/m_elt.c
+++ b/src/machine/m_elt.c
@@ -58,13 +58,13 @@ static void
 elt_vid_off_poll(void *priv)
 {
     cga_t  *cga   = priv;
-    uint8_t hdisp = cga->crtc[1];
+    uint8_t hdisp = cga->crtc[CGA_CRTC_HDISP];
 
     /* Don't display anything.
      * TODO: Do something less stupid to emulate backlight off. */
-    cga->crtc[1] = 0;
+    cga->crtc[CGA_CRTC_HDISP] = 0;
     cga_poll(cga);
-    cga->crtc[1] = hdisp;
+    cga->crtc[CGA_CRTC_HDISP] = hdisp;
 }
 
 static void
diff --git a/src/machine/m_xt_olivetti.c b/src/machine/m_xt_olivetti.c
index acdb77fd1..8e37dce1f 100644
--- a/src/machine/m_xt_olivetti.c
+++ b/src/machine/m_xt_olivetti.c
@@ -1918,7 +1918,7 @@ m19_vid_out(uint16_t addr, uint8_t val, void *priv)
     /* activating plantronics mode */
     if (addr == 0x3dd) {
         /* already in graphics mode */
-        if ((val & 0x30) && (vid->ogc.cga.cgamode & 0x2))
+        if ((val & 0x30) && (vid->ogc.cga.cgamode & CGA_MODE_FLAG_GRAPHICS))
             vid->mode = PLANTRONICS_MODE;
         else
             vid->mode = OLIVETTI_OGC_MODE;
diff --git a/src/machine/m_xt_t1000_vid.c b/src/machine/m_xt_t1000_vid.c
index efad869e1..8811309a0 100644
--- a/src/machine/m_xt_t1000_vid.c
+++ b/src/machine/m_xt_t1000_vid.c
@@ -246,24 +246,24 @@ t1000_text_row80(t1000_t *t1000)
     int      blink;
     uint16_t addr;
     uint8_t  sc;
-    uint16_t ma = (t1000->cga.crtc[13] | (t1000->cga.crtc[12] << 8)) & 0x3fff;
-    uint16_t ca = (t1000->cga.crtc[15] | (t1000->cga.crtc[14] << 8)) & 0x3fff;
+    uint16_t ma = (t1000->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (t1000->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
+    uint16_t ca = (t1000->cga.crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (t1000->cga.crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x3fff;
 
     sc   = (t1000->displine) & 7;
     addr = ((ma & ~1) + (t1000->displine >> 3) * 80) * 2;
     ma += (t1000->displine >> 3) * 80;
 
-    if ((t1000->cga.crtc[10] & 0x60) == 0x20) {
+    if ((t1000->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20) {
         cursorline = 0;
     } else {
-        cursorline = ((t1000->cga.crtc[10] & 0x0F) <= sc) && ((t1000->cga.crtc[11] & 0x0F) >= sc);
+        cursorline = ((t1000->cga.crtc[CGA_CRTC_CURSOR_START] & 0x0F) <= sc) && ((t1000->cga.crtc[CGA_CRTC_CURSOR_END] & 0x0F) >= sc);
     }
     for (uint8_t x = 0; x < 80; x++) {
         chr        = t1000->vram[(addr + 2 * x) & 0x3FFF];
         attr       = t1000->vram[(addr + 2 * x + 1) & 0x3FFF];
-        drawcursor = ((ma == ca) && cursorline && (t1000->cga.cgamode & 8) && (t1000->cga.cgablink & 16));
+        drawcursor = ((ma == ca) && cursorline && (t1000->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && (t1000->cga.cgablink & 16));
 
-        blink = ((t1000->cga.cgablink & 16) && (t1000->cga.cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+        blink = ((t1000->cga.cgablink & 16) && (t1000->cga.cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
 
         if (t1000->video_options & 1)
             bold = boldcols[attr] ? chr : chr + 256;
@@ -272,7 +272,7 @@ t1000_text_row80(t1000_t *t1000)
         if (t1000->video_options & 2)
             bold += 512;
 
-        if (t1000->cga.cgamode & 0x20) /* Blink */
+        if (t1000->cga.cgamode & CGA_MODE_FLAG_BLINK) /* Blink */
         {
             cols[1] = blinkcols[attr][1];
             cols[0] = blinkcols[attr][0];
@@ -307,24 +307,24 @@ t1000_text_row40(t1000_t *t1000)
     int      blink;
     uint16_t addr;
     uint8_t  sc;
-    uint16_t ma = (t1000->cga.crtc[13] | (t1000->cga.crtc[12] << 8)) & 0x3fff;
-    uint16_t ca = (t1000->cga.crtc[15] | (t1000->cga.crtc[14] << 8)) & 0x3fff;
+    uint16_t ma = (t1000->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (t1000->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
+    uint16_t ca = (t1000->cga.crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (t1000->cga.crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x3fff;
 
     sc   = (t1000->displine) & 7;
     addr = ((ma & ~1) + (t1000->displine >> 3) * 40) * 2;
     ma += (t1000->displine >> 3) * 40;
 
-    if ((t1000->cga.crtc[10] & 0x60) == 0x20) {
+    if ((t1000->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20) {
         cursorline = 0;
     } else {
-        cursorline = ((t1000->cga.crtc[10] & 0x0F) <= sc) && ((t1000->cga.crtc[11] & 0x0F) >= sc);
+        cursorline = ((t1000->cga.crtc[CGA_CRTC_CURSOR_START] & 0x0F) <= sc) && ((t1000->cga.crtc[CGA_CRTC_CURSOR_END] & 0x0F) >= sc);
     }
     for (uint8_t x = 0; x < 40; x++) {
         chr        = t1000->vram[(addr + 2 * x) & 0x3FFF];
         attr       = t1000->vram[(addr + 2 * x + 1) & 0x3FFF];
-        drawcursor = ((ma == ca) && cursorline && (t1000->cga.cgamode & 8) && (t1000->cga.cgablink & 16));
+        drawcursor = ((ma == ca) && cursorline && (t1000->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && (t1000->cga.cgablink & 16));
 
-        blink = ((t1000->cga.cgablink & 16) && (t1000->cga.cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+        blink = ((t1000->cga.cgablink & 16) && (t1000->cga.cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
 
         if (t1000->video_options & 1)
             bold = boldcols[attr] ? chr : chr + 256;
@@ -333,7 +333,7 @@ t1000_text_row40(t1000_t *t1000)
         if (t1000->video_options & 2)
             bold += 512;
 
-        if (t1000->cga.cgamode & 0x20) /* Blink */
+        if (t1000->cga.cgamode & CGA_MODE_FLAG_BLINK) /* Blink */
         {
             cols[1] = blinkcols[attr][1];
             cols[0] = blinkcols[attr][0];
@@ -366,7 +366,7 @@ t1000_cgaline6(t1000_t *t1000)
     uint32_t fg = (t1000->cga.cgacol & 0x0F) ? blue : grey;
     uint32_t bg = grey;
 
-    uint16_t ma = (t1000->cga.crtc[13] | (t1000->cga.crtc[12] << 8)) & 0x3fff;
+    uint16_t ma = (t1000->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (t1000->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
 
     addr = ((t1000->displine) & 1) * 0x2000 + (t1000->displine >> 1) * 80 + ((ma & ~1) << 1);
 
@@ -376,7 +376,7 @@ t1000_cgaline6(t1000_t *t1000)
 
         for (uint8_t c = 0; c < 8; c++) {
             ink = (dat & 0x80) ? fg : bg;
-            if (!(t1000->cga.cgamode & 8))
+            if (!(t1000->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE))
                 ink = grey;
             (buffer32->line[t1000->displine])[x * 8 + c] = ink;
             dat                                                       = dat << 1;
@@ -395,7 +395,7 @@ t1000_cgaline4(t1000_t *t1000)
     uint32_t ink1;
     uint16_t addr;
 
-    uint16_t ma = (t1000->cga.crtc[13] | (t1000->cga.crtc[12] << 8)) & 0x3fff;
+    uint16_t ma = (t1000->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (t1000->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
     addr        = ((t1000->displine) & 1) * 0x2000 + (t1000->displine >> 1) * 80 + ((ma & ~1) << 1);
 
     for (uint8_t x = 0; x < 80; x++) {
@@ -404,7 +404,7 @@ t1000_cgaline4(t1000_t *t1000)
 
         for (uint8_t c = 0; c < 4; c++) {
             pattern = (dat & 0xC0) >> 6;
-            if (!(t1000->cga.cgamode & 8))
+            if (!(t1000->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE))
                 pattern = 0;
 
             switch (pattern & 3) {
@@ -479,7 +479,7 @@ t1000_poll(void *priv)
 
             /* Graphics */
             if (t1000->cga.cgamode & 0x02) {
-                if (t1000->cga.cgamode & 0x10)
+                if (t1000->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)
                     t1000_cgaline6(t1000);
                 else
                     t1000_cgaline4(t1000);
@@ -532,7 +532,7 @@ t1000_poll(void *priv)
             video_res_y = T1000_YSIZE;
 
             if (t1000->cga.cgamode & 0x02) {
-                if (t1000->cga.cgamode & 0x10)
+                if (t1000->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)
                     video_bpp = 1;
                 else
                     video_bpp = 2;
diff --git a/src/video/vid_cga.c b/src/video/vid_cga.c
index 0fb1a1402..38dac61c7 100644
--- a/src/video/vid_cga.c
+++ b/src/video/vid_cga.c
@@ -75,7 +75,7 @@ cga_update_latch(cga_t *cga)
 {
     uint32_t lp_latch = cga->displine * cga->crtc[CGA_CRTC_HDISP];
 
-    cga->crtc[0x10] = (lp_latch >> 8) & 0x3f;
+    cga->crtc[CGA_CRTC_LIGHT_PEN_ADDR_HIGH] = (lp_latch >> 8) & 0x3f;
     cga->crtc[CGA_CRTC_LIGHT_PEN_ADDR_LOW] = lp_latch & 0xff;
 }
 
diff --git a/src/video/vid_cga_comp.c b/src/video/vid_cga_comp.c
index 6ad6a6b0a..ca9c2c9df 100644
--- a/src/video/vid_cga_comp.c
+++ b/src/video/vid_cga_comp.c
@@ -135,7 +135,7 @@ update_cga16_color(uint8_t cgamode)
         int left  = (x >> 6) & 15;
         int rc    = right;
         int lc    = left;
-        if ((cgamode & 4) != 0) {
+        if ((cgamode & CGA_MODE_FLAG_BW) != 0) {
             rc = (right & 8) | ((right & 7) != 0 ? 7 : 0);
             lc = (left & 8) | ((left & 7) != 0 ? 7 : 0);
         }
@@ -240,7 +240,7 @@ Composite_Process(uint8_t cgamode, uint8_t border, uint32_t blocks /*, bool doub
     for (uint8_t x = 0; x < 5; ++x)
         OUT(b[x & 3]);
 
-    if ((cgamode & 4) != 0) {
+    if ((cgamode & CGA_MODE_FLAG_BW) != 0) {
         /* Decode */
         i    = temp + 5;
         srgb = TempLine;
diff --git a/src/video/vid_colorplus.c b/src/video/vid_colorplus.c
index d15865c1e..716d35b76 100644
--- a/src/video/vid_colorplus.c
+++ b/src/video/vid_colorplus.c
@@ -173,7 +173,7 @@ colorplus_poll(void *priv)
             } else if (colorplus->control & COLORPLUS_640x200_MODE) {
                 cols[0] = (colorplus->cga.cgacol & 15) | 16;
                 col     = (colorplus->cga.cgacol & 16) ? 24 : 16;
-                if (colorplus->cga.cgamode & 4) {
+                if (colorplus->cga.cgamode & CGA_MODE_FLAG_BW) {
                     cols[1] = col | 3;
                     cols[2] = col | 4;
                     cols[3] = col | 7;
@@ -268,7 +268,7 @@ colorplus_poll(void *priv)
                 colorplus->cga.displine  = 0;
                 colorplus->cga.vsynctime = 16;
                 if (colorplus->cga.crtc[CGA_CRTC_VSYNC]) {
-                    if (colorplus->cga.cgamode & 1)
+                    if (colorplus->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
                         x = (colorplus->cga.crtc[CGA_CRTC_HDISP] << 3) + 16;
                     else
                         x = (colorplus->cga.crtc[CGA_CRTC_HDISP] << 4) + 16;
@@ -288,15 +288,15 @@ colorplus_poll(void *priv)
 
                     video_res_x = xsize - 16;
                     video_res_y = ysize;
-                    if (colorplus->cga.cgamode & 1) {
+                    if (colorplus->cga.cgamode & CGA_MODE_FLAG_HIGHRES) {
                         video_res_x /= 8;
                         video_res_y /= colorplus->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1;
                         video_bpp = 0;
-                    } else if (!(colorplus->cga.cgamode & 2)) {
+                    } else if (!(colorplus->cga.cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                         video_res_x /= 16;
                         video_res_y /= colorplus->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1;
                         video_bpp = 0;
-                    } else if (!(colorplus->cga.cgamode & 16)) {
+                    } else if (!(colorplus->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)) {
                         video_res_x /= 2;
                         video_bpp = 2;
                     } else {
@@ -317,7 +317,7 @@ colorplus_poll(void *priv)
             colorplus->cga.cgastat &= ~1;
         if (colorplus->cga.sc == (colorplus->cga.crtc[CGA_CRTC_CURSOR_START] & 31) || ((colorplus->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && colorplus->cga.sc == ((colorplus->cga.crtc[CGA_CRTC_CURSOR_START] & 31) >> 1)))
             colorplus->cga.cursorvisible = 1;
-        if (colorplus->cga.cgadispon && (colorplus->cga.cgamode & 1)) {
+        if (colorplus->cga.cgadispon && (colorplus->cga.cgamode & CGA_MODE_FLAG_HIGHRES)) {
             for (x = 0; x < (colorplus->cga.crtc[CGA_CRTC_HDISP] << 1); x++)
                 colorplus->cga.charbuffer[x] = colorplus->cga.vram[((colorplus->cga.ma << 1) + x) & 0x3fff];
         }
diff --git a/src/video/vid_compaq_cga.c b/src/video/vid_compaq_cga.c
index 80c6ecb9e..23b7e44df 100644
--- a/src/video/vid_compaq_cga.c
+++ b/src/video/vid_compaq_cga.c
@@ -72,9 +72,9 @@ compaq_cga_recalctimings(compaq_cga_t *self)
     double _dispontime;
     double _dispofftime;
     double disptime;
-    disptime = self->cga.crtc[0] + 1;
+    disptime = self->cga.crtc[CGA_CRTC_HTOTAL] + 1;
 
-    _dispontime  = self->cga.crtc[1];
+    _dispontime  = self->cga.crtc[CGA_CRTC_HDISP];
     _dispofftime = disptime - _dispontime;
     _dispontime *= MDACONST;
     _dispofftime *= MDACONST;
@@ -86,7 +86,7 @@ void
 compaq_cga_poll(void *priv)
 {
     compaq_cga_t *self = (compaq_cga_t *) priv;
-    uint16_t      ca   = (self->cga.crtc[15] | (self->cga.crtc[14] << 8)) & 0x3fff;
+    uint16_t      ca   = (self->cga.crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (self->cga.crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x3fff;
     int           drawcursor;
     int           x;
     int           c;
@@ -102,7 +102,7 @@ compaq_cga_poll(void *priv)
     int           blink     = 0;
 
     /* If in graphics mode or character height is not 13, behave as CGA */
-    if ((self->cga.cgamode & 0x12) || (self->cga.crtc[9] != 13)) {
+    if ((self->cga.cgamode & 0x12) || (self->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] != 13)) {
         overscan_x = overscan_y = 16;
         cga_poll(&self->cga);
         return;
@@ -115,7 +115,7 @@ compaq_cga_poll(void *priv)
         self->cga.cgastat |= 1;
         self->cga.linepos = 1;
         oldsc             = self->cga.sc;
-        if ((self->cga.crtc[8] & 3) == 3)
+        if ((self->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3)
             self->cga.sc = ((self->cga.sc << 1) + self->cga.oddeven) & 7;
         if (self->cga.cgadispon) {
             if (self->cga.displine < self->cga.firstline) {
@@ -129,21 +129,21 @@ compaq_cga_poll(void *priv)
 
             for (c = 0; c < 8; c++) {
                 buffer32->line[self->cga.displine][c] = cols[0];
-                if (self->cga.cgamode & 1)
-                    buffer32->line[self->cga.displine][c + (self->cga.crtc[1] << 3) + 8] = cols[0];
+                if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
+                    buffer32->line[self->cga.displine][c + (self->cga.crtc[CGA_CRTC_HDISP] << 3) + 8] = cols[0];
                 else
-                    buffer32->line[self->cga.displine][c + (self->cga.crtc[1] << 4) + 8] = cols[0];
+                    buffer32->line[self->cga.displine][c + (self->cga.crtc[CGA_CRTC_HDISP] << 4) + 8] = cols[0];
             }
 
-            if (self->cga.cgamode & 1) {
-                for (x = 0; x < self->cga.crtc[1]; x++) {
+            if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES) {
+                for (x = 0; x < self->cga.crtc[CGA_CRTC_HDISP]; x++) {
                     chr        = self->cga.charbuffer[x << 1];
                     attr       = self->cga.charbuffer[(x << 1) + 1];
                     drawcursor = ((self->cga.ma == ca) && self->cga.cursorvisible && self->cga.cursoron);
 
                     if (vflags) {
                         underline = 0;
-                        blink     = ((self->cga.cgablink & 8) && (self->cga.cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+                        blink     = ((self->cga.cgablink & 8) && (self->cga.cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
                     }
 
                     if (vflags && (self->cga.cgamode & 0x80)) {
@@ -152,7 +152,7 @@ compaq_cga_poll(void *priv)
 
                         if ((self->cga.sc == 12) && ((attr & 7) == 1))
                             underline = 1;
-                    } else if (self->cga.cgamode & 0x20) {
+                    } else if (self->cga.cgamode & CGA_MODE_FLAG_BLINK) {
                         cols[1] = (attr & 15) + 16;
                         cols[0] = ((attr >> 4) & 7) + 16;
 
@@ -181,14 +181,14 @@ compaq_cga_poll(void *priv)
                     self->cga.ma++;
                 }
             } else {
-                for (x = 0; x < self->cga.crtc[1]; x++) {
+                for (x = 0; x < self->cga.crtc[CGA_CRTC_HDISP]; x++) {
                     chr        = self->cga.vram[(self->cga.ma << 1) & 0x3fff];
                     attr       = self->cga.vram[((self->cga.ma << 1) + 1) & 0x3fff];
                     drawcursor = ((self->cga.ma == ca) && self->cga.cursorvisible && self->cga.cursoron);
 
                     if (vflags) {
                         underline = 0;
-                        blink     = ((self->cga.cgablink & 8) && (self->cga.cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+                        blink     = ((self->cga.cgablink & 8) && (self->cga.cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
                     }
 
                     if (vflags && (self->cga.cgamode & 0x80)) {
@@ -196,7 +196,7 @@ compaq_cga_poll(void *priv)
                         cols[1] = mdaattr[attr][blink][1];
                         if (self->cga.sc == 12 && (attr & 7) == 1)
                             underline = 1;
-                    } else if (self->cga.cgamode & 0x20) {
+                    } else if (self->cga.cgamode & CGA_MODE_FLAG_BLINK) {
                         cols[1] = (attr & 15) + 16;
                         cols[0] = ((attr >> 4) & 7) + 16;
 
@@ -228,19 +228,19 @@ compaq_cga_poll(void *priv)
         } else {
             cols[0] = (self->cga.cgacol & 15) + 16;
 
-            if (self->cga.cgamode & 1)
-                hline(buffer32, 0, self->cga.displine, (self->cga.crtc[1] << 3) + 16, cols[0]);
+            if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
+                hline(buffer32, 0, self->cga.displine, (self->cga.crtc[CGA_CRTC_HDISP] << 3) + 16, cols[0]);
             else
-                hline(buffer32, 0, self->cga.displine, (self->cga.crtc[1] << 4) + 16, cols[0]);
+                hline(buffer32, 0, self->cga.displine, (self->cga.crtc[CGA_CRTC_HDISP] << 4) + 16, cols[0]);
         }
 
-        if (self->cga.cgamode & 1)
-            x = (self->cga.crtc[1] << 3) + 16;
+        if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
+            x = (self->cga.crtc[CGA_CRTC_HDISP] << 3) + 16;
         else
-            x = (self->cga.crtc[1] << 4) + 16;
+            x = (self->cga.crtc[CGA_CRTC_HDISP] << 4) + 16;
 
         if (self->cga.composite) {
-            if (self->cga.cgamode & 0x10)
+            if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)
                 border = 0x00;
             else
                 border = self->cga.cgacol & 0x0f;
@@ -253,7 +253,7 @@ compaq_cga_poll(void *priv)
             video_process_8(x, self->cga.displine);
 
         self->cga.sc = oldsc;
-        if (self->cga.vc == self->cga.crtc[7] && !self->cga.sc)
+        if (self->cga.vc == self->cga.crtc[CGA_CRTC_VSYNC] && !self->cga.sc)
             self->cga.cgastat |= 8;
         self->cga.displine++;
         if (self->cga.displine >= 500)
@@ -267,10 +267,10 @@ compaq_cga_poll(void *priv)
                 self->cga.cgastat &= ~8;
         }
 
-        if (self->cga.sc == (self->cga.crtc[11] & 31) || ((self->cga.crtc[8] & 3) == 3 && self->cga.sc == ((self->cga.crtc[11] & 31) >> 1))) {
+        if (self->cga.sc == (self->cga.crtc[CGA_CRTC_CURSOR_END] & 31) || ((self->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && self->cga.sc == ((self->cga.crtc[CGA_CRTC_CURSOR_END] & 31) >> 1))) {
             self->cga.cursorvisible  = 0;
         }
-        if ((self->cga.crtc[8] & 3) == 3 && self->cga.sc == (self->cga.crtc[9] >> 1))
+        if ((self->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && self->cga.sc == (self->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] >> 1))
             self->cga.maback = self->cga.ma;
         if (self->cga.vadj) {
             self->cga.sc++;
@@ -279,48 +279,48 @@ compaq_cga_poll(void *priv)
             self->cga.vadj--;
             if (!self->cga.vadj) {
                 self->cga.cgadispon = 1;
-                self->cga.ma = self->cga.maback = (self->cga.crtc[13] | (self->cga.crtc[12] << 8)) & 0x3fff;
+                self->cga.ma = self->cga.maback = (self->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (self->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
                 self->cga.sc                    = 0;
             }
-        } else if (self->cga.sc == self->cga.crtc[9]) {
+        } else if (self->cga.sc == self->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR]) {
             self->cga.maback = self->cga.ma;
             self->cga.sc     = 0;
             oldvc            = self->cga.vc;
             self->cga.vc++;
             self->cga.vc &= 127;
 
-            if (self->cga.vc == self->cga.crtc[6])
+            if (self->cga.vc == self->cga.crtc[CGA_CRTC_VDISP])
                 self->cga.cgadispon = 0;
 
-            if (oldvc == self->cga.crtc[4]) {
+            if (oldvc == self->cga.crtc[CGA_CRTC_VTOTAL]) {
                 self->cga.vc   = 0;
-                self->cga.vadj = self->cga.crtc[5];
+                self->cga.vadj = self->cga.crtc[CGA_CRTC_VTOTAL_ADJUST];
 
                 if (!self->cga.vadj)
                     self->cga.cgadispon = 1;
 
                 if (!self->cga.vadj)
-                    self->cga.ma = self->cga.maback = (self->cga.crtc[13] | (self->cga.crtc[12] << 8)) & 0x3fff;
+                    self->cga.ma = self->cga.maback = (self->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (self->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
 
-                if ((self->cga.crtc[10] & 0x60) == 0x20)
+                if ((self->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20)
                     self->cga.cursoron = 0;
                 else
                     self->cga.cursoron = self->cga.cgablink & 8;
             }
 
-            if (self->cga.vc == self->cga.crtc[7]) {
+            if (self->cga.vc == self->cga.crtc[CGA_CRTC_VSYNC]) {
                 self->cga.cgadispon = 0;
                 self->cga.displine  = 0;
                 self->cga.vsynctime = 16;
 
-                if (self->cga.crtc[7]) {
+                if (self->cga.crtc[CGA_CRTC_VSYNC]) {
                     compaq_cga_log("Lastline %i Firstline %i  %i\n", self->cga.lastline,
                                    self->cga.firstline, self->cga.lastline - self->cga.firstline);
 
-                    if (self->cga.cgamode & 1)
-                        x = (self->cga.crtc[1] << 3) + 16;
+                    if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
+                        x = (self->cga.crtc[CGA_CRTC_HDISP] << 3) + 16;
                     else
-                        x = (self->cga.crtc[1] << 4) + 16;
+                        x = (self->cga.crtc[CGA_CRTC_HDISP] << 4) + 16;
 
                     self->cga.lastline++;
 
@@ -335,7 +335,7 @@ compaq_cga_poll(void *priv)
                         if (!enable_overscan)
                             xs_temp -= 16;
 
-                        if ((self->cga.cgamode & 8) && ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get())) {
+                        if ((self->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get())) {
                             xsize = xs_temp;
                             ysize = ys_temp;
                             set_screen_size(xsize, ysize + (enable_overscan ? 16 : 0));
@@ -356,15 +356,15 @@ compaq_cga_poll(void *priv)
                     if (enable_overscan)
                         xsize -= 16;
                     video_res_y = ysize;
-                    if (self->cga.cgamode & 1) {
+                    if (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES) {
                         video_res_x /= 8;
-                        video_res_y /= self->cga.crtc[9] + 1;
+                        video_res_y /= self->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1;
                         video_bpp = 0;
-                    } else if (!(self->cga.cgamode & 2)) {
+                    } else if (!(self->cga.cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                         video_res_x /= 16;
-                        video_res_y /= self->cga.crtc[9] + 1;
+                        video_res_y /= self->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1;
                         video_bpp = 0;
-                    } else if (!(self->cga.cgamode & 16)) {
+                    } else if (!(self->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS)) {
                         video_res_x /= 2;
                         video_bpp = 2;
                     } else
@@ -385,11 +385,11 @@ compaq_cga_poll(void *priv)
         if (self->cga.cgadispon)
             self->cga.cgastat &= ~1;
 
-        if (self->cga.sc == (self->cga.crtc[10] & 31) || ((self->cga.crtc[8] & 3) == 3 && self->cga.sc == ((self->cga.crtc[10] & 31) >> 1)))
+        if (self->cga.sc == (self->cga.crtc[CGA_CRTC_CURSOR_START] & 31) || ((self->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && self->cga.sc == ((self->cga.crtc[CGA_CRTC_CURSOR_START] & 31) >> 1)))
             self->cga.cursorvisible = 1;
 
-        if (self->cga.cgadispon && (self->cga.cgamode & 1)) {
-            for (x = 0; x < (self->cga.crtc[1] << 1); x++)
+        if (self->cga.cgadispon && (self->cga.cgamode & CGA_MODE_FLAG_HIGHRES)) {
+            for (x = 0; x < (self->cga.crtc[CGA_CRTC_HDISP] << 1); x++)
                 self->cga.charbuffer[x] = self->cga.vram[((self->cga.ma << 1) + x) & 0x3fff];
         }
     }
@@ -445,7 +445,7 @@ compaq_cga_init(const device_t *info)
     cga_palette        = (self->cga.rgb_type << 1);
     cgapal_rebuild();
 
-    self->cga.crtc[9] = 13;
+    self->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] = 13;
 
     return self;
 }
@@ -464,7 +464,7 @@ compaq_cga_speed_changed(void *priv)
 {
     compaq_cga_t *self = (compaq_cga_t *) priv;
 
-    if (self->cga.crtc[9] == 13) /* Character height */
+    if (self->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] == 13) /* Character height */
         compaq_cga_recalctimings(self);
     else
         cga_recalctimings(&self->cga);
diff --git a/src/video/vid_f82c425.c b/src/video/vid_f82c425.c
index c607cda14..a8fd2227b 100644
--- a/src/video/vid_f82c425.c
+++ b/src/video/vid_f82c425.c
@@ -362,27 +362,27 @@ f82c425_text_row(f82c425_t *f82c425)
     int      blink;
     uint16_t addr;
     uint8_t  sc;
-    uint16_t ma      = (f82c425->cga.crtc[0x0d] | (f82c425->cga.crtc[0x0c] << 8)) & 0x3fff;
+    uint16_t ma      = (f82c425->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (f82c425->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
     uint16_t ca      = (f82c425->cga.crtc[0x0f] | (f82c425->cga.crtc[0x0e] << 8)) & 0x3fff;
-    uint8_t  sl      = f82c425->cga.crtc[9] + 1;
-    int      columns = f82c425->cga.crtc[1];
+    uint8_t  sl      = f82c425->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1;
+    int      columns = f82c425->cga.crtc[CGA_CRTC_HDISP];
 
     sc   = (f82c425->displine) & 7;
     addr = ((ma & ~1) + (f82c425->displine >> 3) * columns) * 2;
     ma += (f82c425->displine >> 3) * columns;
 
-    if ((f82c425->cga.crtc[0x0a] & 0x60) == 0x20) {
+    if ((f82c425->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) == 0x20) {
         cursorline = 0;
     } else {
-        cursorline = ((f82c425->cga.crtc[0x0a] & 0x0F) <= sc) && ((f82c425->cga.crtc[0x0b] & 0x0F) >= sc);
+        cursorline = ((f82c425->cga.crtc[CGA_CRTC_CURSOR_START] & 0x0F) <= sc) && ((f82c425->cga.crtc[CGA_CRTC_CURSOR_END] & 0x0F) >= sc);
     }
 
     for (int x = 0; x < columns; x++) {
         chr        = f82c425->vram[(addr + 2 * x) & 0x3FFF];
         attr       = f82c425->vram[(addr + 2 * x + 1) & 0x3FFF];
-        drawcursor = ((ma == ca) && cursorline && (f82c425->cga.cgamode & 0x8) && (f82c425->cga.cgablink & 0x10));
+        drawcursor = ((ma == ca) && cursorline && (f82c425->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && (f82c425->cga.cgablink & 0x10));
 
-        blink = ((f82c425->cga.cgablink & 0x10) && (f82c425->cga.cgamode & 0x20) && (attr & 0x80) && !drawcursor);
+        blink = ((f82c425->cga.cgablink & 0x10) && (f82c425->cga.cgamode & CGA_MODE_FLAG_BLINK) && (attr & 0x80) && !drawcursor);
 
         if (drawcursor) {
             colors[0] = smartmap[~attr & 0xff][0];
@@ -418,7 +418,7 @@ f82c425_cgaline6(f82c425_t *f82c425)
     uint8_t  dat;
     uint16_t addr;
 
-    uint16_t ma = (f82c425->cga.crtc[0x0d] | (f82c425->cga.crtc[0x0c] << 8)) & 0x3fff;
+    uint16_t ma = (f82c425->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (f82c425->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
 
     addr = ((f82c425->displine) & 1) * 0x2000 + (f82c425->displine >> 1) * 80 + ((ma & ~1) << 1);
 
@@ -442,7 +442,7 @@ f82c425_cgaline4(f82c425_t *f82c425)
     uint8_t  pattern;
     uint16_t addr;
 
-    uint16_t ma = (f82c425->cga.crtc[0x0d] | (f82c425->cga.crtc[0x0c] << 8)) & 0x3fff;
+    uint16_t ma = (f82c425->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (f82c425->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
     addr        = ((f82c425->displine) & 1) * 0x2000 + (f82c425->displine >> 1) * 80 + ((ma & ~1) << 1);
 
     for (uint8_t x = 0; x < 80; x++) {
@@ -526,7 +526,7 @@ f82c425_poll(void *priv)
             f82c425->displine = 0;
             f82c425->cga.cgastat &= ~8;
             f82c425->dispon = 1;
-        } else if (f82c425->displine == (f82c425->cga.crtc[9] + 1) * f82c425->cga.crtc[6]) {
+        } else if (f82c425->displine == (f82c425->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1) * f82c425->cga.crtc[CGA_CRTC_VDISP]) {
             /* Start of VSYNC */
             f82c425->cga.cgastat |= 8;
             f82c425->dispon = 0;
diff --git a/src/video/vid_nga.c b/src/video/vid_nga.c
index 7a30bf173..2eb94220a 100644
--- a/src/video/vid_nga.c
+++ b/src/video/vid_nga.c
@@ -56,12 +56,12 @@ nga_recalctimings(nga_t *nga)
     double _dispofftime;
     double disptime;
 
-    if (nga->cga.cgamode & 1) {
-        disptime    = nga->cga.crtc[0] + 1;
-        _dispontime = nga->cga.crtc[1];
+    if (nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES) {
+        disptime    = nga->cga.crtc[CGA_CRTC_HTOTAL] + 1;
+        _dispontime = nga->cga.crtc[CGA_CRTC_HDISP];
     } else {
-        disptime    = (nga->cga.crtc[0] + 1) << 1;
-        _dispontime = nga->cga.crtc[1] << 1;
+        disptime    = (nga->cga.crtc[CGA_CRTC_HTOTAL] + 1) << 1;
+        _dispontime = nga->cga.crtc[CGA_CRTC_HDISP] << 1;
     }
 
     _dispofftime = disptime - _dispontime;
@@ -148,7 +148,7 @@ nga_poll(void *priv)
 {
     nga_t *nga = (nga_t *) priv;
     /* set cursor position in memory */
-    uint16_t ca = (nga->cga.crtc[15] | (nga->cga.crtc[14] << 8)) & 0x3fff;
+    uint16_t ca = (nga->cga.crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (nga->cga.crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x3fff;
     int      drawcursor;
     int      x;
     int      c;
@@ -164,7 +164,7 @@ nga_poll(void *priv)
     int      oldsc;
 
     /* graphic mode and not high-res modes */
-    if ((nga->cga.cgamode & 2) && !(nga->cga.cgamode & 0x40)) {
+    if ((nga->cga.cgamode & CGA_MODE_FLAG_GRAPHICS) && !(nga->cga.cgamode & 0x40)) {
         /* standard cga mode */
         cga_poll(&nga->cga);
         return;
@@ -176,7 +176,7 @@ nga_poll(void *priv)
             nga->cga.linepos = 1;
             oldsc            = nga->cga.sc;
             /* if interlaced */
-            if ((nga->cga.crtc[8] & 3) == 3)
+            if ((nga->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3)
                 nga->cga.sc = ((nga->cga.sc << 1) + nga->cga.oddeven) & 7;
             if (nga->cga.cgadispon) {
                 if (nga->cga.displine < nga->cga.firstline) {
@@ -185,11 +185,11 @@ nga_poll(void *priv)
                 }
                 nga->cga.lastline = nga->cga.displine;
                 /* 80-col */
-                if ((nga->cga.cgamode & 1) && !(nga->cga.cgamode & 2)) {
+                if ((nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES) && !(nga->cga.cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                     /* for each text column */
-                    for (x = 0; x < nga->cga.crtc[1]; x++) {
+                    for (x = 0; x < nga->cga.crtc[CGA_CRTC_HDISP]; x++) {
                         /* video output enabled */
-                        if (nga->cga.cgamode & 8) {
+                        if (nga->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) {
                             /* character */
                             chr = nga->cga.charbuffer[x << 1];
                             /* text attributes */
@@ -201,7 +201,7 @@ nga_poll(void *priv)
                         /* set foreground */
                         cols[1] = (attr & 15) + 16;
                         /* blink active */
-                        if (nga->cga.cgamode & 0x20) {
+                        if (nga->cga.cgamode & CGA_MODE_FLAG_BLINK) {
                             cols[0] = ((attr >> 4) & 7) + 16;
                             /* attribute 7 active and not cursor */
                             if ((nga->cga.cgablink & 8) && (attr & 0x80) && !nga->cga.drawcursor) {
@@ -224,10 +224,10 @@ nga_poll(void *priv)
                     }
                 }
                 /* 40-col */
-                else if (!(nga->cga.cgamode & 2)) {
+                else if (!(nga->cga.cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                     /* for each text column */
-                    for (x = 0; x < nga->cga.crtc[1]; x++) {
-                        if (nga->cga.cgamode & 8) {
+                    for (x = 0; x < nga->cga.crtc[CGA_CRTC_HDISP]; x++) {
+                        if (nga->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) {
                             chr  = nga->cga.vram[((nga->cga.ma << 1) & 0x3fff) + nga->base];
                             attr = nga->cga.vram[(((nga->cga.ma << 1) + 1) & 0x3fff) + nga->base];
                         } else {
@@ -237,7 +237,7 @@ nga_poll(void *priv)
                         /* set foreground */
                         cols[1] = (attr & 15) + 16;
                         /* blink active */
-                        if (nga->cga.cgamode & 0x20) {
+                        if (nga->cga.cgamode & CGA_MODE_FLAG_BLINK) {
                             cols[0] = ((attr >> 4) & 7) + 16;
                             if ((nga->cga.cgablink & 8) && (attr & 0x80) && !nga->cga.drawcursor) {
                                 /* set blinking */
@@ -262,7 +262,7 @@ nga_poll(void *priv)
                     /* high res modes */
                     if (nga->cga.cgamode & 0x40) {
                         /* 640x400x2 mode */
-                        if (nga->cga.cgamode & 0x4 || nga->cga.cgamode & 0x10) {
+                        if (nga->cga.cgamode & 0x4 || nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS) {
                             /*
                              * Scanlines are read in the following order:
                              * 0b8000-0b9f3f even scans (0,4,...)
@@ -277,7 +277,7 @@ nga_poll(void *priv)
                         } else {
                             cols[0] = (nga->cga.cgacol & 15) | 16;
                             col     = (nga->cga.cgacol & 16) ? 24 : 16;
-                            if (nga->cga.cgamode & 4) {
+                            if (nga->cga.cgamode & CGA_MODE_FLAG_BW) {
                                 cols[1] = col | 3; /* Cyan */
                                 cols[2] = col | 4; /* Red */
                                 cols[3] = col | 7; /* White */
@@ -306,11 +306,11 @@ nga_poll(void *priv)
                     }
 
                     /* for each text column */
-                    for (x = 0; x < nga->cga.crtc[1]; x++) {
+                    for (x = 0; x < nga->cga.crtc[CGA_CRTC_HDISP]; x++) {
                         /* video out */
-                        if (nga->cga.cgamode & 8) {
+                        if (nga->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) {
                             /* 640x400x2 */
-                            if (nga->cga.cgamode & 0x4 || nga->cga.cgamode & 0x10) {
+                            if (nga->cga.cgamode & 0x4 || nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES_GRAPHICS) {
                                 /* read two bytes at a time */
                                 dat = (nga->cga.vram[((nga->cga.ma << 1) & 0x1fff) + dat2] << 8) | nga->cga.vram[((nga->cga.ma << 1) & 0x1fff) + dat2 + 1];
                                 /* each pixel is represented by one bit, so draw 16 pixels at a time */
@@ -347,26 +347,26 @@ nga_poll(void *priv)
                 /* nga specific */
                 cols[0] = ((nga->cga.cgamode & 0x12) == 0x12) ? 0 : (nga->cga.cgacol & 15) + 16;
                 /* 80-col */
-                if (nga->cga.cgamode & 1) {
-                    hline(buffer32, 0, (nga->cga.displine << 1), ((nga->cga.crtc[1] << 3) + 16) << 2, cols[0]);
-                    hline(buffer32, 0, (nga->cga.displine << 1) + 1, ((nga->cga.crtc[1] << 3) + 16) << 2, cols[0]);
+                if (nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES) {
+                    hline(buffer32, 0, (nga->cga.displine << 1), ((nga->cga.crtc[CGA_CRTC_HDISP] << 3) + 16) << 2, cols[0]);
+                    hline(buffer32, 0, (nga->cga.displine << 1) + 1, ((nga->cga.crtc[CGA_CRTC_HDISP] << 3) + 16) << 2, cols[0]);
                 } else {
-                    hline(buffer32, 0, (nga->cga.displine << 1), ((nga->cga.crtc[1] << 4) + 16) << 2, cols[0]);
-                    hline(buffer32, 0, (nga->cga.displine << 1) + 1, ((nga->cga.crtc[1] << 4) + 16) << 2, cols[0]);
+                    hline(buffer32, 0, (nga->cga.displine << 1), ((nga->cga.crtc[CGA_CRTC_HDISP] << 4) + 16) << 2, cols[0]);
+                    hline(buffer32, 0, (nga->cga.displine << 1) + 1, ((nga->cga.crtc[CGA_CRTC_HDISP] << 4) + 16) << 2, cols[0]);
                 }
             }
 
-            if (nga->cga.cgamode & 1)
+            if (nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
                 /* set screen width */
-                x = (nga->cga.crtc[1] << 3) + 16;
+                x = (nga->cga.crtc[CGA_CRTC_HDISP] << 3) + 16;
             else
-                x = (nga->cga.crtc[1] << 4) + 16;
+                x = (nga->cga.crtc[CGA_CRTC_HDISP] << 4) + 16;
 
             video_process_8(x, nga->cga.displine);
 
             nga->cga.sc = oldsc;
             /* vertical sync */
-            if (nga->cga.vc == nga->cga.crtc[7] && !nga->cga.sc)
+            if (nga->cga.vc == nga->cga.crtc[CGA_CRTC_VSYNC] && !nga->cga.sc)
                 nga->cga.cgastat |= 8;
             nga->cga.displine++;
             if (nga->cga.displine >= 720)
@@ -380,7 +380,7 @@ nga_poll(void *priv)
             nga->lineff ^= 1;
 
             /* text mode or 640x400x2 */
-            if (nga->lineff && !((nga->cga.cgamode & 1) && (nga->cga.cgamode & 0x40))) {
+            if (nga->lineff && !((nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES) && (nga->cga.cgamode & 0x40))) {
                 nga->cga.ma = nga->cga.maback;
                 /* 640x400x4 */
             } else {
@@ -390,11 +390,11 @@ nga_poll(void *priv)
                         nga->cga.cgastat &= ~8;
                 }
                 /* cursor stop scanline */
-                if (nga->cga.sc == (nga->cga.crtc[11] & 31) || ((nga->cga.crtc[8] & 3) == 3 && nga->cga.sc == ((nga->cga.crtc[11] & 31) >> 1))) {
+                if (nga->cga.sc == (nga->cga.crtc[CGA_CRTC_CURSOR_END] & 31) || ((nga->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && nga->cga.sc == ((nga->cga.crtc[CGA_CRTC_CURSOR_END] & 31) >> 1))) {
                     nga->cga.cursorvisible  = 0;
                 }
                 /* interlaced and max scanline per char reached */
-                if ((nga->cga.crtc[8] & 3) == 3 && nga->cga.sc == (nga->cga.crtc[9] >> 1))
+                if ((nga->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && nga->cga.sc == (nga->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] >> 1))
                     nga->cga.maback = nga->cga.ma;
 
                 if (nga->cga.vadj) {
@@ -405,12 +405,12 @@ nga_poll(void *priv)
                     if (!nga->cga.vadj) {
                         nga->cga.cgadispon = 1;
                         /* change start of displayed page (crtc 12-13) */
-                        nga->cga.ma = nga->cga.maback = (nga->cga.crtc[13] | (nga->cga.crtc[12] << 8)) & 0x7fff;
+                        nga->cga.ma = nga->cga.maback = (nga->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (nga->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x7fff;
                         nga->cga.sc                   = 0;
                     }
                     /* nga specific */
                     /* end of character line reached */
-                } else if (nga->cga.sc == nga->cga.crtc[9] || ((nga->cga.crtc[8] & 3) == 3 && nga->cga.sc == (nga->cga.crtc[9] >> 1))) {
+                } else if (nga->cga.sc == nga->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] || ((nga->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && nga->cga.sc == (nga->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] >> 1))) {
                     nga->cga.maback = nga->cga.ma;
                     nga->cga.sc     = 0;
                     oldvc           = nga->cga.vc;
@@ -418,21 +418,21 @@ nga_poll(void *priv)
                     nga->cga.vc &= 127;
 
                     /* lines of character displayed */
-                    if (nga->cga.vc == nga->cga.crtc[6])
+                    if (nga->cga.vc == nga->cga.crtc[CGA_CRTC_VDISP])
                         nga->cga.cgadispon = 0;
 
                     /* total vertical lines */
-                    if (oldvc == nga->cga.crtc[4]) {
+                    if (oldvc == nga->cga.crtc[CGA_CRTC_VTOTAL]) {
                         nga->cga.vc = 0;
                         /* adjust vertical lines */
-                        nga->cga.vadj = nga->cga.crtc[5];
+                        nga->cga.vadj = nga->cga.crtc[CGA_CRTC_VTOTAL_ADJUST];
                         if (!nga->cga.vadj) {
                             nga->cga.cgadispon = 1;
                             /* change start of displayed page (crtc 12-13) */
-                            nga->cga.ma = nga->cga.maback = (nga->cga.crtc[13] | (nga->cga.crtc[12] << 8)) & 0x7fff;
+                            nga->cga.ma = nga->cga.maback = (nga->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (nga->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x7fff;
                         }
                         /* cursor start */
-                        switch (nga->cga.crtc[10] & 0x60) {
+                        switch (nga->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) {
                             case 0x20:
                                 nga->cga.cursoron = 0;
                                 break;
@@ -445,18 +445,18 @@ nga_poll(void *priv)
                         }
                     }
                     /* vertical line position */
-                    if (nga->cga.vc == nga->cga.crtc[7]) {
+                    if (nga->cga.vc == nga->cga.crtc[CGA_CRTC_VSYNC]) {
                         nga->cga.cgadispon = 0;
                         nga->cga.displine  = 0;
                         /* nga specific */
                         nga->cga.vsynctime = 16;
                         /* vsync pos */
-                        if (nga->cga.crtc[7]) {
-                            if (nga->cga.cgamode & 1)
+                        if (nga->cga.crtc[CGA_CRTC_VSYNC]) {
+                            if (nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
                                 /* set screen width */
-                                x = (nga->cga.crtc[1] << 3) + 16;
+                                x = (nga->cga.crtc[CGA_CRTC_HDISP] << 3) + 16;
                             else
-                                x = (nga->cga.crtc[1] << 4) + 16;
+                                x = (nga->cga.crtc[CGA_CRTC_HDISP] << 4) + 16;
                             nga->cga.lastline++;
 
                             xs_temp = x;
@@ -471,7 +471,7 @@ nga_poll(void *priv)
                                 if (!enable_overscan)
                                     xs_temp -= 16;
 
-                                if ((nga->cga.cgamode & 8) && ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get())) {
+                                if ((nga->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get())) {
                                     xsize = xs_temp;
                                     ysize = ys_temp;
                                     set_screen_size(xsize, ysize + (enable_overscan ? 16 : 0));
@@ -493,14 +493,14 @@ nga_poll(void *priv)
                             video_res_x = xsize;
                             video_res_y = ysize;
                             /* 80-col */
-                            if ((nga->cga.cgamode & 1) && !(nga->cga.cgamode & 0x40)) {
+                            if ((nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES) && !(nga->cga.cgamode & 0x40)) {
                                 video_res_x /= 8;
-                                video_res_y /= (nga->cga.crtc[9] + 1) * 2;
+                                video_res_y /= (nga->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1) * 2;
                                 video_bpp = 0;
                                 /* 40-col */
-                            } else if (!(nga->cga.cgamode & 2)) {
+                            } else if (!(nga->cga.cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                                 video_res_x /= 16;
-                                video_res_y /= (nga->cga.crtc[9] + 1) * 2;
+                                video_res_y /= (nga->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1) * 2;
                                 video_bpp = 0;
                             } else if (nga->cga.cgamode & 0x40) {
                                 video_res_x /= 8;
@@ -523,13 +523,13 @@ nga_poll(void *priv)
                     nga->cga.cgastat &= ~1;
 
                 /* enable cursor if its scanline was reached */
-                if (nga->cga.sc == (nga->cga.crtc[10] & 31) || ((nga->cga.crtc[8] & 3) == 3 && nga->cga.sc == ((nga->cga.crtc[10] & 31) >> 1)))
+                if (nga->cga.sc == (nga->cga.crtc[CGA_CRTC_CURSOR_START] & 31) || ((nga->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && nga->cga.sc == ((nga->cga.crtc[CGA_CRTC_CURSOR_START] & 31) >> 1)))
                     nga->cga.cursorvisible = 1;
             }
             /* 80-columns */
-            if (nga->cga.cgadispon && (nga->cga.cgamode & 1)) {
+            if (nga->cga.cgadispon && (nga->cga.cgamode & CGA_MODE_FLAG_HIGHRES)) {
                 /* for each character per line */
-                for (x = 0; x < (nga->cga.crtc[1] << 1); x++)
+                for (x = 0; x < (nga->cga.crtc[CGA_CRTC_HDISP] << 1); x++)
                     nga->cga.charbuffer[x] = nga->cga.vram[(((nga->cga.ma << 1) + x) & 0x3fff) + nga->base];
             }
         }
diff --git a/src/video/vid_ogc.c b/src/video/vid_ogc.c
index afbc778a6..bc54499b2 100644
--- a/src/video/vid_ogc.c
+++ b/src/video/vid_ogc.c
@@ -65,12 +65,12 @@ ogc_recalctimings(ogc_t *ogc)
     double _dispofftime;
     double disptime;
 
-    if (ogc->cga.cgamode & 1) {
-        disptime    = ogc->cga.crtc[0] + 1;
-        _dispontime = ogc->cga.crtc[1];
+    if (ogc->cga.cgamode & CGA_MODE_FLAG_HIGHRES) {
+        disptime    = ogc->cga.crtc[CGA_CRTC_HTOTAL] + 1;
+        _dispontime = ogc->cga.crtc[CGA_CRTC_HDISP];
     } else {
-        disptime    = (ogc->cga.crtc[0] + 1) << 1;
-        _dispontime = ogc->cga.crtc[1] << 1;
+        disptime    = (ogc->cga.crtc[CGA_CRTC_HTOTAL] + 1) << 1;
+        _dispontime = ogc->cga.crtc[CGA_CRTC_HDISP] << 1;
     }
 
     _dispofftime = disptime - _dispontime;
@@ -201,7 +201,7 @@ void
 ogc_poll(void *priv)
 {
     ogc_t   *ogc = (ogc_t *) priv;
-    uint16_t ca  = (ogc->cga.crtc[15] | (ogc->cga.crtc[14] << 8)) & 0x3fff;
+    uint16_t ca  = (ogc->cga.crtc[CGA_CRTC_CURSOR_ADDR_LOW] | (ogc->cga.crtc[CGA_CRTC_CURSOR_ADDR_HIGH] << 8)) & 0x3fff;
     int      drawcursor;
     int      x;
     int      c;
@@ -220,7 +220,7 @@ ogc_poll(void *priv)
     // composito colore appare blu scuro
 
     /* graphic mode and not mode 40h */
-    if (!(ogc->ctrl_3de & 0x1 || !(ogc->cga.cgamode & 2))) {
+    if (!(ogc->ctrl_3de & 0x1 || !(ogc->cga.cgamode & CGA_MODE_FLAG_GRAPHICS))) {
         /* standard cga mode */
         cga_poll(&ogc->cga);
         return;
@@ -231,7 +231,7 @@ ogc_poll(void *priv)
             ogc->cga.cgastat |= 1;
             ogc->cga.linepos = 1;
             oldsc            = ogc->cga.sc;
-            if ((ogc->cga.crtc[8] & 3) == 3)
+            if ((ogc->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3)
                 ogc->cga.sc = ((ogc->cga.sc << 1) + ogc->cga.oddeven) & 7;
             if (ogc->cga.cgadispon) {
                 if (ogc->cga.displine < ogc->cga.firstline) {
@@ -240,11 +240,11 @@ ogc_poll(void *priv)
                 }
                 ogc->cga.lastline = ogc->cga.displine;
                 /* 80-col */
-                if (ogc->cga.cgamode & 1) {
+                if (ogc->cga.cgamode & CGA_MODE_FLAG_HIGHRES) {
                     /* for each text column */
-                    for (x = 0; x < ogc->cga.crtc[1]; x++) {
+                    for (x = 0; x < ogc->cga.crtc[CGA_CRTC_HDISP]; x++) {
                         /* video output enabled */
-                        if (ogc->cga.cgamode & 8) {
+                        if (ogc->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) {
                             /* character */
                             chr = ogc->cga.charbuffer[x << 1];
                             /* text attributes */
@@ -263,7 +263,7 @@ ogc_poll(void *priv)
                         /* set foreground */
                         cols[1] = (attr & 15) + 16;
                         /* blink active */
-                        if (ogc->cga.cgamode & 0x20) {
+                        if (ogc->cga.cgamode & CGA_MODE_FLAG_BLINK) {
                             cols[0] = ((attr >> 4) & 7) + 16;
                             /* attribute 7 active and not cursor */
                             if ((ogc->cga.cgablink & 8) && (attr & 0x80) && !ogc->cga.drawcursor) {
@@ -293,9 +293,9 @@ ogc_poll(void *priv)
                     }
                 }
                 /* 40-col */
-                else if (!(ogc->cga.cgamode & 2)) {
-                    for (x = 0; x < ogc->cga.crtc[1]; x++) {
-                        if (ogc->cga.cgamode & 8) {
+                else if (!(ogc->cga.cgamode & CGA_MODE_FLAG_GRAPHICS)) {
+                    for (x = 0; x < ogc->cga.crtc[CGA_CRTC_HDISP]; x++) {
+                        if (ogc->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) {
                             chr  = ogc->cga.vram[((ogc->cga.ma << 1) & 0x3fff) + ogc->base];
                             attr = ogc->cga.vram[(((ogc->cga.ma << 1) + 1) & 0x3fff) + ogc->base];
                         } else {
@@ -312,7 +312,7 @@ ogc_poll(void *priv)
                         /* set foreground */
                         cols[1] = (attr & 15) + 16;
                         /* blink active */
-                        if (ogc->cga.cgamode & 0x20) {
+                        if (ogc->cga.cgamode & CGA_MODE_FLAG_BLINK) {
                             cols[0] = ((attr >> 4) & 7) + 16;
                             if ((ogc->cga.cgablink & 8) && (attr & 0x80) && !ogc->cga.drawcursor) {
                                 /* set blinking */
@@ -352,9 +352,9 @@ ogc_poll(void *priv)
                         cols[1] = (ogc->cga.cgacol & 15) + 16;
                     }
 
-                    for (x = 0; x < ogc->cga.crtc[1]; x++) {
+                    for (x = 0; x < ogc->cga.crtc[CGA_CRTC_HDISP]; x++) {
                         /* video out */
-                        if (ogc->cga.cgamode & 8) {
+                        if (ogc->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) {
                             dat = (ogc->cga.vram[((ogc->cga.ma << 1) & 0x1fff) + dat2] << 8) | ogc->cga.vram[((ogc->cga.ma << 1) & 0x1fff) + dat2 + 1];
                         } else {
                             dat = 0;
@@ -370,22 +370,22 @@ ogc_poll(void *priv)
             } else {
                 /* ogc specific */
                 cols[0] = ((ogc->cga.cgamode & 0x12) == 0x12) ? 0 : (ogc->cga.cgacol & 15) + 16;
-                if (ogc->cga.cgamode & 1)
-                    hline(buffer32, 0, ogc->cga.displine, ((ogc->cga.crtc[1] << 3) + 16) << 2, cols[0]);
+                if (ogc->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
+                    hline(buffer32, 0, ogc->cga.displine, ((ogc->cga.crtc[CGA_CRTC_HDISP] << 3) + 16) << 2, cols[0]);
                 else
-                    hline(buffer32, 0, ogc->cga.displine, ((ogc->cga.crtc[1] << 4) + 16) << 2, cols[0]);
+                    hline(buffer32, 0, ogc->cga.displine, ((ogc->cga.crtc[CGA_CRTC_HDISP] << 4) + 16) << 2, cols[0]);
             }
 
             /* 80 columns */
-            if (ogc->cga.cgamode & 1)
-                x = (ogc->cga.crtc[1] << 3) + 16;
+            if (ogc->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
+                x = (ogc->cga.crtc[CGA_CRTC_HDISP] << 3) + 16;
             else
-                x = (ogc->cga.crtc[1] << 4) + 16;
+                x = (ogc->cga.crtc[CGA_CRTC_HDISP] << 4) + 16;
 
             video_process_8(x, ogc->cga.displine);
 
             ogc->cga.sc = oldsc;
-            if (ogc->cga.vc == ogc->cga.crtc[7] && !ogc->cga.sc)
+            if (ogc->cga.vc == ogc->cga.crtc[CGA_CRTC_VSYNC] && !ogc->cga.sc)
                 ogc->cga.cgastat |= 8;
             ogc->cga.displine++;
             if (ogc->cga.displine >= 720)
@@ -405,10 +405,10 @@ ogc_poll(void *priv)
                     if (!ogc->cga.vsynctime)
                         ogc->cga.cgastat &= ~8;
                 }
-                if (ogc->cga.sc == (ogc->cga.crtc[11] & 31) || ((ogc->cga.crtc[8] & 3) == 3 && ogc->cga.sc == ((ogc->cga.crtc[11] & 31) >> 1))) {
+                if (ogc->cga.sc == (ogc->cga.crtc[CGA_CRTC_CURSOR_END] & 31) || ((ogc->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && ogc->cga.sc == ((ogc->cga.crtc[CGA_CRTC_CURSOR_END] & 31) >> 1))) {
                     ogc->cga.cursorvisible  = 0;
                 }
-                if ((ogc->cga.crtc[8] & 3) == 3 && ogc->cga.sc == (ogc->cga.crtc[9] >> 1))
+                if ((ogc->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && ogc->cga.sc == (ogc->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] >> 1))
                     ogc->cga.maback = ogc->cga.ma;
                 if (ogc->cga.vadj) {
                     ogc->cga.sc++;
@@ -417,28 +417,28 @@ ogc_poll(void *priv)
                     ogc->cga.vadj--;
                     if (!ogc->cga.vadj) {
                         ogc->cga.cgadispon = 1;
-                        ogc->cga.ma = ogc->cga.maback = (ogc->cga.crtc[13] | (ogc->cga.crtc[12] << 8)) & 0x3fff;
+                        ogc->cga.ma = ogc->cga.maback = (ogc->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (ogc->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
                         ogc->cga.sc                   = 0;
                     }
                     // potrebbe dare problemi con composito
-                } else if (ogc->cga.sc == ogc->cga.crtc[9] || ((ogc->cga.crtc[8] & 3) == 3 && ogc->cga.sc == (ogc->cga.crtc[9] >> 1))) {
+                } else if (ogc->cga.sc == ogc->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] || ((ogc->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && ogc->cga.sc == (ogc->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] >> 1))) {
                     ogc->cga.maback = ogc->cga.ma;
                     ogc->cga.sc     = 0;
                     oldvc           = ogc->cga.vc;
                     ogc->cga.vc++;
                     ogc->cga.vc &= 127;
 
-                    if (ogc->cga.vc == ogc->cga.crtc[6])
+                    if (ogc->cga.vc == ogc->cga.crtc[CGA_CRTC_VDISP])
                         ogc->cga.cgadispon = 0;
 
-                    if (oldvc == ogc->cga.crtc[4]) {
+                    if (oldvc == ogc->cga.crtc[CGA_CRTC_VTOTAL]) {
                         ogc->cga.vc   = 0;
-                        ogc->cga.vadj = ogc->cga.crtc[5];
+                        ogc->cga.vadj = ogc->cga.crtc[CGA_CRTC_VTOTAL_ADJUST];
                         if (!ogc->cga.vadj) {
                             ogc->cga.cgadispon = 1;
-                            ogc->cga.ma = ogc->cga.maback = (ogc->cga.crtc[13] | (ogc->cga.crtc[12] << 8)) & 0x3fff;
+                            ogc->cga.ma = ogc->cga.maback = (ogc->cga.crtc[CGA_CRTC_START_ADDR_LOW] | (ogc->cga.crtc[CGA_CRTC_START_ADDR_HIGH] << 8)) & 0x3fff;
                         }
-                        switch (ogc->cga.crtc[10] & 0x60) {
+                        switch (ogc->cga.crtc[CGA_CRTC_CURSOR_START] & 0x60) {
                             case 0x20:
                                 ogc->cga.cursoron = 0;
                                 break;
@@ -450,16 +450,16 @@ ogc_poll(void *priv)
                                 break;
                         }
                     }
-                    if (ogc->cga.vc == ogc->cga.crtc[7]) {
+                    if (ogc->cga.vc == ogc->cga.crtc[CGA_CRTC_VSYNC]) {
                         ogc->cga.cgadispon = 0;
                         ogc->cga.displine  = 0;
                         /* ogc specific */
-                        ogc->cga.vsynctime = (ogc->cga.crtc[3] >> 4) + 1;
-                        if (ogc->cga.crtc[7]) {
-                            if (ogc->cga.cgamode & 1)
-                                x = (ogc->cga.crtc[1] << 3) + 16;
+                        ogc->cga.vsynctime = (ogc->cga.crtc[CGA_CRTC_HSYNC_WIDTH] >> 4) + 1;
+                        if (ogc->cga.crtc[CGA_CRTC_VSYNC]) {
+                            if (ogc->cga.cgamode & CGA_MODE_FLAG_HIGHRES)
+                                x = (ogc->cga.crtc[CGA_CRTC_HDISP] << 3) + 16;
                             else
-                                x = (ogc->cga.crtc[1] << 4) + 16;
+                                x = (ogc->cga.crtc[CGA_CRTC_HDISP] << 4) + 16;
                             ogc->cga.lastline++;
 
                             xs_temp = x;
@@ -474,7 +474,7 @@ ogc_poll(void *priv)
                                 if (!enable_overscan)
                                     xs_temp -= 16;
 
-                                if ((ogc->cga.cgamode & 8) && ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get())) {
+                                if ((ogc->cga.cgamode & CGA_MODE_FLAG_VIDEO_ENABLE) && ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get())) {
                                     xsize = xs_temp;
                                     ysize = ys_temp;
                                     set_screen_size(xsize, ysize + (enable_overscan ? 16 : 0));
@@ -496,14 +496,14 @@ ogc_poll(void *priv)
                             video_res_x = xsize;
                             video_res_y = ysize;
                             /* 80-col */
-                            if (ogc->cga.cgamode & 1) {
+                            if (ogc->cga.cgamode & CGA_MODE_FLAG_HIGHRES) {
                                 video_res_x /= 8;
-                                video_res_y /= (ogc->cga.crtc[9] + 1) * 2;
+                                video_res_y /= (ogc->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1) * 2;
                                 video_bpp = 0;
                                 /* 40-col */
-                            } else if (!(ogc->cga.cgamode & 2)) {
+                            } else if (!(ogc->cga.cgamode & CGA_MODE_FLAG_GRAPHICS)) {
                                 video_res_x /= 16;
-                                video_res_y /= (ogc->cga.crtc[9] + 1) * 2;
+                                video_res_y /= (ogc->cga.crtc[CGA_CRTC_MAX_SCANLINE_ADDR] + 1) * 2;
                                 video_bpp = 0;
                             } else if (!(ogc->ctrl_3de & 1)) {
                                 video_res_y /= 2;
@@ -524,12 +524,12 @@ ogc_poll(void *priv)
                 if (ogc->cga.cgadispon)
                     ogc->cga.cgastat &= ~1;
 
-                if (ogc->cga.sc == (ogc->cga.crtc[10] & 31) || ((ogc->cga.crtc[8] & 3) == 3 && ogc->cga.sc == ((ogc->cga.crtc[10] & 31) >> 1)))
+                if (ogc->cga.sc == (ogc->cga.crtc[CGA_CRTC_CURSOR_START] & 31) || ((ogc->cga.crtc[CGA_CRTC_INTERLACE] & 3) == 3 && ogc->cga.sc == ((ogc->cga.crtc[CGA_CRTC_CURSOR_START] & 31) >> 1)))
                     ogc->cga.cursorvisible = 1;
             }
             /* 80-columns */
-            if (ogc->cga.cgadispon && (ogc->cga.cgamode & 1)) {
-                for (x = 0; x < (ogc->cga.crtc[1] << 1); x++)
+            if (ogc->cga.cgadispon && (ogc->cga.cgamode & CGA_MODE_FLAG_HIGHRES)) {
+                for (x = 0; x < (ogc->cga.crtc[CGA_CRTC_HDISP] << 1); x++)
                     ogc->cga.charbuffer[x] = ogc->cga.vram[(((ogc->cga.ma << 1) + x) & 0x3fff) + ogc->base];
             }
         }