From 9b9f1a261056dbb288210583768bc6b99d9af1fc Mon Sep 17 00:00:00 2001
From: TC1995 <mariogplayer90@gmail.com>
Date: Mon, 11 Aug 2025 22:55:47 +0200
Subject: [PATCH] 8514/A (and XGA) compatible refresh rate fixes.

Correct the refresh rates of the 8514/A compatibles and XGA cards to match their real world rates.
---
 src/video/vid_ati_mach8.c | 46 ++++++++++++++++++++-------------------
 src/video/vid_svga.c      | 11 +++++-----
 2 files changed, 30 insertions(+), 27 deletions(-)

diff --git a/src/video/vid_ati_mach8.c b/src/video/vid_ati_mach8.c
index 32b466740..45a69ffab 100644
--- a/src/video/vid_ati_mach8.c
+++ b/src/video/vid_ati_mach8.c
@@ -2928,10 +2928,12 @@ mach_recalctimings(svga_t *svga)
 
         dev->h_disp_time = dev->hdisp >> 3;
 
-        svga->clock_8514 = (cpuclock * (double) (1ULL << 32)) / svga->getclock((mach->accel.clock_sel >> 2) & 0x0f, svga->clock_gen);
+        svga->clock_8514 = (cpuclock * (double) (1ULL << 32)) / svga->getclock((mach->accel.clock_sel >> 2) & 0x0f, svga->clock_gen) / 2;
         if (mach->accel.clock_sel & 0x40)
             svga->clock_8514 *= 2;
 
+        mach_log("8514/A clock sel=%x, divide reg ibm=%02x, divide reg vga=%02x.\n", clock_sel, mach->accel.clock_sel & 0x40, mach->regs[0xb8] & 0xc0);
+
         if (dev->interlace)
             dev->dispend >>= 1;
 
@@ -3060,29 +3062,29 @@ mach_recalctimings(svga_t *svga)
         if (!svga->scrblank && (svga->crtc[0x17] & 0x80) && svga->attr_palette_enable) {
             mach_log("GDCREG5=%02x, ATTR10=%02x, ATI B0 bit 5=%02x, ON=%d.\n",
                      svga->gdcreg[5] & 0x60, svga->attrregs[0x10] & 0x40, mach->regs[0xb0] & 0x20, dev->on);
+            svga->clock = (cpuclock * (double) (1ULL << 32)) / svga->getclock(clock_sel, svga->clock_gen);
+            mach_log("VGA clock sel=%x, divide reg=%02x.\n", clock_sel, mach->regs[0xb8] & 0xc0);
+            if (ATI_MACH32) {
+                if (mach->regs[0xb8] & 0x40)
+                    svga->clock *= 2;
+            } else {
+                switch (mach->regs[0xb8] & 0xc0) {
+                    case 0x40:
+                        svga->clock *= 2;
+                        break;
+                    case 0x80:
+                        svga->clock *= 3;
+                        break;
+                    case 0xc0:
+                        svga->clock *= 4;
+                        break;
+
+                    default:
+                        break;
+                }
+            }
             if ((svga->gdcreg[6] & 0x01) || (svga->attrregs[0x10] & 0x01)) {
                 if ((svga->gdcreg[5] & 0x40) || (svga->attrregs[0x10] & 0x40) || (mach->regs[0xb0] & 0x20)) {
-                    svga->clock = (cpuclock * (double) (1ULL << 32)) / svga->getclock(clock_sel, svga->clock_gen);
-                    mach_log("VGA clock=%02x.\n", mach->regs[0xa7] & 0x80);
-                    if (ATI_MACH32) {
-                        if (mach->regs[0xb8] & 0x40)
-                            svga->clock *= 2;
-                    } else {
-                        switch (mach->regs[0xb8] & 0xc0) {
-                            case 0x40:
-                                svga->clock *= 2;
-                                break;
-                            case 0x80:
-                                svga->clock *= 3;
-                                break;
-                            case 0xc0:
-                                svga->clock *= 4;
-                                break;
-
-                            default:
-                                break;
-                        }
-                    }
                     svga->map8 = svga->pallook;
                     mach_log("Lowres=%x, seqreg[1]bit3=%x.\n", svga->lowres, svga->seqregs[1] & 8);
                     if (svga->lowres)
diff --git a/src/video/vid_svga.c b/src/video/vid_svga.c
index 113a8984f..caed7113f 100644
--- a/src/video/vid_svga.c
+++ b/src/video/vid_svga.c
@@ -799,9 +799,10 @@ svga_recalctimings(svga_t *svga)
 
             if ((svga->bpp <= 8) || ((svga->gdcreg[5] & 0x60) <= 0x20)) {
                 if ((svga->gdcreg[5] & 0x60) == 0x00) {
-                    if (svga->seqregs[1] & 8) /*Low res (320)*/
+                    if (svga->seqregs[1] & 8) { /*Low res (320)*/
                         svga->render = svga_render_4bpp_lowres;
-                    else
+                        svga_log("4 bpp low res.\n");
+                    } else
                         svga->render = svga_render_4bpp_highres;
                 } else if ((svga->gdcreg[5] & 0x60) == 0x20) {
                     if (svga->seqregs[1] & 8) { /*Low res (320)*/
@@ -1045,11 +1046,11 @@ svga_recalctimings(svga_t *svga)
     crtcconst = svga->clock * svga->char_width;
     if (ibm8514_active && (svga->dev8514 != NULL)) {
         if (dev->on)
-            crtcconst8514 = svga->clock_8514;
+            crtcconst8514 = svga->clock_8514 * 8;
     }
     if (xga_active && (svga->xga != NULL)) {
         if (xga->on)
-            crtcconst_xga = svga->clock_xga;
+            crtcconst_xga = svga->clock_xga * svga->char_width;
     }
 
 #ifdef ENABLE_SVGA_LOG
@@ -1093,7 +1094,6 @@ svga_recalctimings(svga_t *svga)
         if (dev->on) {
             disptime8514 = dev->h_total;
             _dispontime8514 = dev->h_disp_time;
-            svga_log("HTOTAL=%d, HDISP=%d.\n", dev->h_total, dev->h_disp);
         }
     }
 
@@ -1135,6 +1135,7 @@ svga_recalctimings(svga_t *svga)
         case 1: /*Plus 8514/A*/
             if (dev->on) {
                 _dispofftime8514 = disptime8514 - _dispontime8514;
+                svga_log("DISPTIME8514=%lf, off=%lf, DISPONTIME8514=%lf, CRTCCONST8514=%lf.\n", disptime8514, _dispofftime8514, _dispontime8514, crtcconst8514);
                 _dispontime8514 *= crtcconst8514;
                 _dispofftime8514 *= crtcconst8514;