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ide: compensate for INT 13h code that counts sectors without regard for

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track boundaries
This commit is contained in:
Jonathan Campbell 2013-10-26 19:01:31 -07:00
parent 5e9476ebbb
commit a94e72ee86
1 changed files with 30 additions and 1 deletions
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31
src/hardware/ide.cpp
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@ -1168,14 +1168,43 @@ void IDE_EmuINT13DiskReadByBIOS(unsigned char disk,unsigned int cyl,unsigned int
if (dev->type == IDE_TYPE_HDD) {
IDEATADevice *ata = (IDEATADevice*)dev;
static bool vm86_warned = false;
static bool int13_fix_wrap_warned = false;
bool vm86 = IDE_CPU_Is_Vm86();
if ((ata->bios_disk_index-2) == (disk-0x80)) {
imageDisk *dsk = ata->getBIOSdisk();
/* HACK: src/ints/bios_disk.cpp implementation doesn't correctly
* wrap sector numbers across tracks. it fullfills the read
* by counting sectors and reading from C,H,S+i which means
* that if the OS assumes the ability to read across track
* boundaries (as Windows 95 does) we will get invalid
* sector numbers, which in turn fouls up our emulation.
*
* Windows 95 OSR2 for example, will happily ask for 63
* sectors starting at C/H/S 30/9/42 without regard for
* track boundaries. */
if (sect > dsk->sectors) {
if (!int13_fix_wrap_warned) {
fprintf(stderr,"INT 13h implementation warning: we were given over-large sector number.\n");
fprintf(stderr,"This is normally the fault of DOSBox INT 13h emulation that counts sectors\n");
fprintf(stderr,"without consideration of track boundaries\n");
int13_fix_wrap_warned = true;
}
do {
sect -= dsk->sectors;
if ((++head) >= dsk->heads) {
head -= dsk->heads;
cyl++;
}
} while (sect > dsk->sectors);
}
/* translate BIOS INT 13h geometry to IDE geometry */
if (ata->headshr != 0) {
unsigned long lba;
imageDisk *dsk = ata->getBIOSdisk();
if (dsk == NULL) return;
lba = (head * dsk->sectors) + (cyl * dsk->sectors * dsk->heads) + sect - 1;
sect = (lba % ata->sects) + 1;