Skip to content

Commit

Permalink
Round up when autodetecting cylinders for a flat disk image, and roun…
Browse files Browse the repository at this point in the history 
…d up when remapping that for IDE geometry
  • Loading branch information
@joncampbell123
joncampbell123 committed Mar 9, 2024
1 parent 864cf7e commit a933f3e
Show file tree
Hide file tree
Showing 2 changed files with 52 additions and 63 deletions.
8 changes: 6 additions & 2 deletions src/dos/dos_programs.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6613,7 +6613,9 @@ class IMGMOUNT : public Program {
/* auto-fill: head/cylinder count */
if (sizes[3]/*cylinders*/ == 0 && sizes[2]/*heads*/ == 0) {
sizes[2] = 16; /* typical hard drive, unless a very old drive */
sizes[3]/*cylinders*/ = (Bitu)((uint64_t)sectors / (uint64_t)sizes[2]/*heads*/ / (uint64_t)sizes[1]/*sectors/track*/);
sizes[3]/*cylinders*/ =
(Bitu)(((uint64_t)sectors + ((uint64_t)sizes[2]/*heads*/ * (uint64_t)sizes[1]/*sectors/track*/) - (uint64_t)1u) /
((uint64_t)sizes[2]/*heads*/ * (uint64_t)sizes[1]/*sectors/track*/));

if (IS_PC98_ARCH) {
/* TODO: PC-98 has its own issues with a 4096-cylinder limit */
Expand All @@ -6628,7 +6630,9 @@ class IMGMOUNT : public Program {
if (sizes[2] >= 256) sizes[2] = 255;

/* and recompute cylinders */
sizes[3]/*cylinders*/ = (Bitu)((uint64_t)sectors / (uint64_t)sizes[2]/*heads*/ / (uint64_t)sizes[1]/*sectors/track*/);
sizes[3]/*cylinders*/ =
(Bitu)(((uint64_t)sectors + ((uint64_t)sizes[2]/*heads*/ * (uint64_t)sizes[1]/*sectors/track*/) - (uint64_t)1u) /
((uint64_t)sizes[2]/*heads*/ * (uint64_t)sizes[1]/*sectors/track*/));
}
}
}
Expand Down
107 changes: 46 additions & 61 deletions src/hardware/ide.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -240,7 +240,7 @@ class IDEATADevice:public IDEDevice {
virtual bool increment_current_address(Bitu count=1);
public:
Bitu multiple_sector_max,multiple_sector_count;
Bitu heads,sects,cyls,headshr,progress_count;
Bitu heads,sects,cyls,progress_count;
Bitu phys_heads,phys_sects,phys_cyls;
unsigned char sector[512 * 128] = {};
Bitu sector_i,sector_total;
Expand Down Expand Up @@ -2594,7 +2594,6 @@ IDEATADevice::IDEATADevice(IDEController *c,unsigned char disk_index,bool _slave
: IDEDevice(c,_slave), id_serial("8086"), id_firmware_rev("8086"), id_model("DOSBox-X IDE disk"), bios_disk_index(disk_index) {
sector_i = sector_total = 0;

headshr = 0;
type = IDE_TYPE_HDD;
multiple_sector_max = sizeof(sector) / 512;
multiple_sector_count = 1;
Expand Down Expand Up @@ -2634,67 +2633,53 @@ void IDEATAPICDROMDevice::update_from_cdrom() {
}

void IDEATADevice::update_from_biosdisk() {
imageDisk *dsk = getBIOSdisk();
if (dsk == NULL) {
LOG_MSG("WARNING: IDE update from BIOS disk failed, disk not available\n");
return;
}
imageDisk *dsk = getBIOSdisk();
if (dsk == NULL) {
LOG_MSG("WARNING: IDE update from BIOS disk failed, disk not available\n");
return;
}

headshr = 0;
geo_translate = false;
cyls = dsk->cylinders;
heads = dsk->heads;
sects = dsk->sectors;

/* One additional correction: The disk image is probably using BIOS-style geometry
translation (such as C/H/S 1024/64/63) which is impossible given that the IDE
standard only allows up to 16 heads. So we have to translate the geometry. */
while (heads > 16 && (heads & 1) == 0) {
cyls <<= 1U;
heads >>= 1U;
headshr++;
}
geo_translate = false;
cyls = dsk->cylinders;
heads = dsk->heads;
sects = dsk->sectors;

if (heads > 16) {
geo_translate = true;

/* One additional correction: The disk image is probably using BIOS-style geometry
translation (such as C/H/S 1024/64/63) which is impossible given that the IDE
standard only allows up to 16 heads. So we have to translate the geometry. */
while (heads > 16 && (heads & 1) == 0)
heads >>= 1U;

/* If we can't divide the heads down, then pick a LBA-like mapping that is good enough.
* Note that if what we pick does not evenly map to the INT 13h geometry, and the partition
* contained within is not an LBA type FAT16/FAT32 partition, then Windows 95's IDE driver
* will ignore this device and fall back to using INT 13h. For user convenience we will
* print a warning to reminder the user of exactly that. */
if (heads > 16) {
sects = 63;
heads = 16;
}

/* If we can't divide the heads down, then pick a LBA-like mapping that is good enough.
* Note that if what we pick does not evenly map to the INT 13h geometry, and the partition
* contained within is not an LBA type FAT16/FAT32 partition, then Windows 95's IDE driver
* will ignore this device and fall back to using INT 13h. For user convenience we will
* print a warning to reminder the user of exactly that. */
if (heads > 16) {
unsigned long tmp;

geo_translate = true;

tmp = heads * cyls * sects;
sects = 63;
heads = 16;
cyls = (tmp + ((63 * 16) - 1)) / (63 * 16);
LOG_MSG("WARNING: Unable to reduce heads to 16 and below\n");
LOG_MSG("If at all possible, please consider using INT 13h geometry with a head\n");
LOG_MSG("count that is easier to map to the BIOS, like 240 heads or 128 heads/track.\n");
LOG_MSG("Some OSes, such as Windows 95, will not enable their 32-bit IDE driver if\n");
LOG_MSG("a clean mapping does not exist between IDE and BIOS geometry.\n");
LOG_MSG("Mapping BIOS DISK C/H/S %u/%u/%u as IDE %u/%u/%u (non-straightforward mapping)\n",
(unsigned int)dsk->cylinders,
(unsigned int)dsk->heads,
(unsigned int)dsk->sectors,
(unsigned int)cyls,
(unsigned int)heads,
(unsigned int)sects);
}
else {
LOG_MSG("Mapping BIOS DISK C/H/S %u/%u/%u as IDE %u/%u/%u\n",
(unsigned int)dsk->cylinders,
(unsigned int)dsk->heads,
(unsigned int)dsk->sectors,
(unsigned int)cyls,
(unsigned int)heads,
(unsigned int)sects);
}
{
uint64_t tmp = ((uint64_t)dsk->diskSizeK << (uint64_t)10) / (uint64_t)dsk->sector_size;
cyls = (tmp + (uint64_t)(sects * heads) - (uint64_t)1) / ((uint64_t)(sects * heads));
}

LOG_MSG("Mapping BIOS DISK C/H/S %u/%u/%u as IDE %u/%u/%u\n",
(unsigned int)dsk->cylinders,
(unsigned int)dsk->heads,
(unsigned int)dsk->sectors,
(unsigned int)cyls,
(unsigned int)heads,
(unsigned int)sects);
}

phys_heads = heads;
phys_sects = sects;
phys_cyls = cyls;
phys_heads = heads;
phys_sects = sects;
phys_cyls = cyls;
}

void IDE_Auto(signed char &index,bool &slave) {
Expand Down Expand Up @@ -3197,7 +3182,7 @@ void IDE_EmuINT13DiskReadByBIOS(unsigned char disk,unsigned int cyl,unsigned int
}

/* translate BIOS INT 13h geometry to IDE geometry */
if (ata->headshr != 0 || ata->geo_translate) {
if (ata->geo_translate) {
unsigned long lba;

if (dsk == NULL) return;
Expand Down

0 comments on commit a933f3e

Please sign in to comment.