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More documentation on VPCEXT opcodes, as requested

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This commit is contained in:
RichardG867
2020-07-27 12:24:31 -03:00
parent 8262c7faae
commit 0b8bd4e610
1 changed files with 22 additions and 9 deletions
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31
src/cpu/386_ops.h
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@@ -214,7 +214,7 @@ static int opVPCEXT(uint32_t fetchdat)
time_t now;
struct tm *tm;
if (!is_vpc)
if (!is_vpc) /* only emulate this on Virtual PC machines */
return ILLEGAL(fetchdat);
cpu_state.pc += 2;
@@ -222,16 +222,19 @@ static int opVPCEXT(uint32_t fetchdat)
b1 = fetchdat & 0xff;
b2 = (fetchdat >> 8) & 0xff;
/* a lot of these opcodes (which?) return illegal instruction in user mode */
ILLEGAL_ON(CPL > 0);
CLOCK_CYCLES(1);
/* 0f 3f 03 xx opcodes are mostly related to the host clock, so fetch it now */
if (b1 == 0x03) {
(void)time(&now);
tm = localtime(&now);
}
if ((b1 == 0x07) && (b2 == 0x0b)) {
/* 0f 3f 07 0b: unknown, EDX output depends on EAX input */
switch (EAX) {
case 0x00000000:
EDX = 0x00000003;
@@ -254,46 +257,56 @@ static int opVPCEXT(uint32_t fetchdat)
default:
EDX = 0x00000000;
if (EAX > 0x00000012)
if (EAX > 0x00000012) /* unknown EAX values set zero flag */
cpu_state.flags &= ~(Z_FLAG);
}
} else if ((b1 == 0x03) && (b2 == 0x00)) {
/* 0f 3f 03 00: host time in BCD */
EDX = BCD8(tm->tm_hour);
ECX = BCD8(tm->tm_min);
EAX = BCD8(tm->tm_sec);
} else if ((b1 == 0x03) && (b2 == 0x01)) {
/* 0f 3f 03 00: host date in BCD */
EDX = BCD8(tm->tm_year % 100);
ECX = BCD8(tm->tm_mon + 1);
EAX = BCD8(tm->tm_mday);
cent = (((tm->tm_year - (tm->tm_year % 100)) / 100) % 4);
cent = (((tm->tm_year - (tm->tm_year % 100)) / 100) % 4); /* Sunday = 0 */
EBX = ((tm->tm_mday + tm->tm_mon + (tm->tm_year % 100) + cent + 3) % 7);
} else if ((b1 == 0x03) && (b2 == 0x03)) {
/* 0f 3f 03 03: host time in binary */
EDX = tm->tm_hour;
ECX = tm->tm_min;
EAX = tm->tm_sec;
} else if ((b1 == 0x03) && (b2 == 0x04)) {
/* 0f 3f 03 04: host date in binary */
EDX = 1900 + tm->tm_year;
ECX = tm->tm_mon + 1;
EBX = tm->tm_mday;
} else if ((b1 == 0x03) && (b2 == 0x05)) {
/* 0f 3f 03 05: unknown */
EBX = 0x0000000F;
ECX = 0x0000000A;
} else if ((b1 == 0x03) && (b2 == 0x06)) {
/* Some kind of timestamp. BX jumps around very quickly, CX not so much. */
/* 0f 3f 03 06: some kind of timestamp. BX jumps around very quickly, CX not so much. */
EBX = 0x00000000;
ECX = 0x00000000;
} else if ((b1 == 0x03) && (b2 >= 0x07)) {
/* 0f 3f 03 07+: set zero flag */
cpu_state.flags &= ~(Z_FLAG);
} else if ((b1 == 0x0a) && (b2 == 0x00)) {
/* 0f 3f 0a 00: memory size in KB */
EAX = mem_size;
} else if ((b1 == 0x11) && (b2 == 0x00))
} else if ((b1 == 0x11) && (b2 == 0x00)) {
/* 0f 3f 11 00: unknown, set EAX to 0 */
EAX = 0x00000000;
else if ((b1 == 0x11) && (b2 == 0x01)) {
} else if ((b1 == 0x11) && (b2 == 0x01)) {
/* 0f 3f 11 00: unknown, set EAX to 0 and set zero flag */
EAX = 0x00000000;
cpu_state.flags &= ~(Z_FLAG);
} else if ((b1 == 0x11) && (b2 == 0x02))
; /* Do nothing */
else {
} else if ((b1 == 0x11) && (b2 == 0x02)) {
/* 0f 3f 11 02: unknown, no-op */
} else {
/* other unknown opcodes: illegal instruction */
cpu_state.pc = cpu_state.oldpc;
pclog("Illegal VPCEXT %08X (%02X %02X)\n", fetchdat, b1, b2);