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Support for alternate IBM EGA Address

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(Disabled behind ifdef because while it's a thing, you need a custom BIOS to use it)
This commit is contained in:
Jasmine Iwanek
2025-05-26 18:38:53 -04:00
parent 7f8cfc2aa7
commit 77f1c62aee
2 changed files with 115 additions and 7 deletions
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2
src/include/86box/vid_ega.h
View File

@@ -148,6 +148,8 @@ typedef struct ega_t {
card should not attempt to display anything. */
void (*render_override)(void *priv);
void * priv_parent;
uint8_t alt_addr; /* 0 for 0x3XX range, 1 for 0x2XX range */
} ega_t;
#endif

120
src/video/vid_ega.c
View File

@@ -72,7 +72,7 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
uint8_t gdcmask = (ega_type == EGA_SUPEREGA) ? 0xff : 0x0f;
uint8_t crtcmask = (atype == EGA_SUPEREGA) ? 0xff : 0x1f;
if (((addr & 0xfff0) == 0x3d0 || (addr & 0xfff0) == 0x3b0) && !(ega->miscout & 1))
if (((((addr & 0xfff0) == 0x3d0) || ((addr & 0xfff0) == 0x2d0)) || (((addr & 0xfff0) == 0x3b0) || ((addr & 0xfff0) == 0x2b0))) && !(ega->miscout & 1))
addr ^= 0x60;
switch (addr) {
@@ -94,7 +94,9 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
}
break;
case 0x2c0:
case 0x3c0:
case 0x2c1:
case 0x3c1:
if (atype == EGA_SUPEREGA)
val &= 0x7f; /* Bit 7 indicates the flipflop status (read only) */
@@ -139,6 +141,7 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
}
ega->attrff ^= 1;
break;
case 0x2c2:
case 0x3c2:
o = ega->miscout;
egaswitchread = (val & 0xc) >> 2;
@@ -148,9 +151,15 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
ega->miscout = val;
ega->overscan_color = ega->vres ? pallook16[ega->attrregs[0x11] & 0x0f] :
pallook64[ega->attrregs[0x11] & 0x3f];
io_removehandler(0x03a0, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
uint16_t base_addr = 0x03a0;
#ifdef EGA_ALT_ADDR_SUPPORT
if (ega->alt_addr == 1)
base_addr = 0x02a0;
#endif
io_removehandler(base_addr, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
if (!(val & 1))
io_sethandler(0x03a0, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
io_sethandler(base_addr, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
ega_recalctimings(ega);
if ((type == EGA_TYPE_COMPAQ) && !(val & 0x02))
mem_mapping_disable(&ega->mapping);
@@ -172,9 +181,11 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
break;
}
break;
case 0x2c4:
case 0x3c4:
ega->seqaddr = val;
break;
case 0x2c5:
case 0x3c5:
o = ega->seqregs[ega->seqaddr & 0xf];
ega->seqregs[ega->seqaddr & 0xf] = val;
@@ -201,13 +212,16 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
break;
}
break;
case 0x2c6:
case 0x3c6:
if (type == EGA_TYPE_COMPAQ)
ega->ctl_mode = val;
break;
case 0x2ce:
case 0x3ce:
ega->gdcaddr = val;
break;
case 0x2cf:
case 0x3cf:
ega->gdcreg[ega->gdcaddr & gdcmask] = val;
switch (ega->gdcaddr & gdcmask) {
@@ -264,14 +278,18 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
break;
}
break;
case 0x2d0:
case 0x3d0:
case 0x2d4:
case 0x3d4:
if (ega->chipset)
ega->crtcreg = val & 0x3f;
else
ega->crtcreg = val;
return;
case 0x2d1:
case 0x3d1:
case 0x2d5:
case 0x3d5: {
int idx = ega->crtcreg;
@@ -322,7 +340,7 @@ ega_in(uint16_t addr, void *priv)
uint8_t gdcmask = (atype == EGA_SUPEREGA) ? 0xff : 0x0f;
uint8_t crtcmask = (atype == EGA_SUPEREGA) ? 0xff : 0x1f;
if (((addr & 0xfff0) == 0x3d0 || (addr & 0xfff0) == 0x3b0) && !(ega->miscout & 1))
if (((((addr & 0xfff0) == 0x3d0) || ((addr & 0xfff0) == 0x2d0)) || (((addr & 0xfff0) == 0x3b0) || ((addr & 0xfff0) == 0x2b0))) && !(ega->miscout & 1))
addr ^= 0x60;
switch (addr) {
@@ -343,7 +361,9 @@ ega_in(uint16_t addr, void *priv)
}
break;
case 0x2c0:
case 0x3c0:
case 0x2c1:
case 0x3c1:
if (type == EGA_TYPE_OTHER) {
int data = (atype == EGA_SUPEREGA) ? (ega->attrff & 1) : (addr & 1);
@@ -356,9 +376,11 @@ ega_in(uint16_t addr, void *priv)
ret = (ret & 0x3f) | (ega->attrff ? 0x80 : 0x00);
}
break;
case 0x2c2:
case 0x3c2:
ret = (egaswitches & (8 >> egaswitchread)) ? 0x10 : 0x00;
break;
case 0x2c4:
case 0x3c4:
if (type == EGA_TYPE_OTHER) {
if (atype == EGA_SUPEREGA)
@@ -367,6 +389,7 @@ ega_in(uint16_t addr, void *priv)
ret = ega->seqaddr;
}
break;
case 0x2c5:
case 0x3c5:
if (type == EGA_TYPE_OTHER) {
if ((ega->seqaddr & 0x0f) > 0x04)
@@ -375,18 +398,22 @@ ega_in(uint16_t addr, void *priv)
ret = ega->seqregs[ega->seqaddr & 0xf];
}
break;
case 0x2c6:
case 0x3c6:
if (type == EGA_TYPE_COMPAQ)
ret = ega->ctl_mode;
break;
case 0x2c8:
case 0x3c8:
if (type == EGA_TYPE_OTHER)
ret = 2;
break;
case 0x2cc:
case 0x3cc:
if (type == EGA_TYPE_OTHER)
ret = ega->miscout;
break;
case 0x2ce:
case 0x3ce:
if (ega_type == EGA_TYPE_OTHER) {
ret = ega->gdcaddr;
@@ -397,6 +424,7 @@ ega_in(uint16_t addr, void *priv)
}
}
break;
case 0x2cf:
case 0x3cf:
if (type == EGA_TYPE_OTHER) {
switch (ega->gdcaddr & gdcmask) {
@@ -421,7 +449,9 @@ ega_in(uint16_t addr, void *priv)
}
}
break;
case 0x2d0:
case 0x3d0:
case 0x2d4:
case 0x3d4:
if (ega_type == EGA_TYPE_OTHER) {
ret = ega->crtcreg;
@@ -432,7 +462,9 @@ ega_in(uint16_t addr, void *priv)
}
}
break;
case 0x2d1:
case 0x3d1:
case 0x2d5:
case 0x3d5:
switch (ega->crtcreg & crtcmask) {
case 0xc:
@@ -467,6 +499,7 @@ ega_in(uint16_t addr, void *priv)
break;
}
break;
case 0x2da:
case 0x3da:
ega->attrff = 0;
if (type == EGA_TYPE_COMPAQ) {
@@ -1464,7 +1497,12 @@ ega_init(ega_t *ega, int monitor_type, int is_mono)
}
}
io_sethandler(0x03a0, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
uint16_t base_addr = 0x03a0;
#ifdef EGA_ALT_ADDR_SUPPORT
if (ega->alt_addr == 1)
base_addr = 0x02a0;
#endif
io_sethandler(base_addr, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
} else {
for (uint16_t c = 0; c < 256; c++) {
pallook64[c] = makecol32(((c >> 2) & 1) * 0xaa, ((c >> 1) & 1) * 0xaa, (c & 1) * 0xaa);
@@ -1619,7 +1657,15 @@ ega_standalone_init(const device_t *info)
mem_mapping_add(&ega->mapping, 0xa0000, 0x20000, ega_read, NULL, NULL, ega_write, NULL, NULL, NULL, MEM_MAPPING_EXTERNAL, ega);
if (ega_type == EGA_TYPE_COMPAQ)
mem_mapping_disable(&ega->mapping);
io_sethandler(0x03c0, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
uint16_t addr = 0x03c0;
#ifdef EGA_ALT_ADDR_SUPPORT
if (ega_type == EGA_TYPE_IBM) {
addr = device_get_config_hex16("base");
if (addr == 0x02c0)
ega->alt_addr = 1;
}
#endif
io_sethandler(addr, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
if (ega->chipset) {
io_sethandler(0x01ce, 0x0002, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
@@ -1699,6 +1745,66 @@ ega_speed_changed(void *priv)
0 = Switch closed (ON);
1 = Switch open (OFF). */
static const device_config_t ega_ibm_config[] = {
// clang-format off
{
.name = "memory",
.description = "Memory size",
.type = CONFIG_SELECTION,
.default_string = NULL,
.default_int = 256,
.file_filter = NULL,
.spinner = { 0 },
.selection = {
{ .description = "32 KB", .value = 32 },
{ .description = "64 KB", .value = 64 },
{ .description = "128 KB", .value = 128 },
{ .description = "256 KB", .value = 256 },
{ .description = "" }
},
.bios = { { 0 } }
},
{
.name = "monitor_type",
.description = "Monitor type",
.type = CONFIG_SELECTION,
.default_string = NULL,
.default_int = 9,
.file_filter = NULL,
.spinner = { 0 },
.selection = {
{ .description = "Monochrome (5151/MDA) (white)", .value = 0x0B | (DISPLAY_WHITE << 4) },
{ .description = "Monochrome (5151/MDA) (green)", .value = 0x0B | (DISPLAY_GREEN << 4) },
{ .description = "Monochrome (5151/MDA) (amber)", .value = 0x0B | (DISPLAY_AMBER << 4) },
{ .description = "Color 40x25 (5153/CGA)", .value = 0x06 },
{ .description = "Color 80x25 (5153/CGA)", .value = 0x07 },
{ .description = "Enhanced Color - Normal Mode (5154/ECD)", .value = 0x08 },
{ .description = "Enhanced Color - Enhanced Mode (5154/ECD)", .value = 0x09 },
{ .description = "" }
},
.bios = { { 0 } }
},
#ifdef EGA_ALT_ADDR_SUPPORT
{
.name = "base",
.description = "Address",
.type = CONFIG_HEX16,
.default_string = NULL,
.default_int = 0x03c0,
.file_filter = NULL,
.spinner = { 0 },
.selection = {
{ .description = "0x3C0", .value = 0x03c0 },
{ .description = "0x2C0", .value = 0x02c0 },
{ .description = "" }
},
.bios = { { 0 } }
},
#endif
{ .name = "", .description = "", .type = CONFIG_END }
// clang-format on
};
static const device_config_t ega_config[] = {
// clang-format off
{
@@ -1753,7 +1859,7 @@ const device_t ega_device = {
.available = ega_standalone_available,
.speed_changed = ega_speed_changed,
.force_redraw = NULL,
.config = ega_config
.config = ega_ibm_config
};
const device_t cpqega_device = {