Interrupts Page
This page contains a listing of all the Interrupts Mentioned on my "How to Read and Write to a Hard Disk" page. All Interrupt Text is from the "Interrupt List" by Ralf Brown. There may be more information here than you need to use them, but I figured I would include the whole thing from each section. I recommend that you download the Interrupt List. I'm not exactly sure where I got it, but I don't believe it's very difficult to find.
Interrupt 13h, section AH=41h
--------d-1341--BX55AA-----------------------
INT 13 - IBM/MS INT 13 Extensions - INSTALLATION CHECK
AH = 41h
BX = 55AAh
DL = drive (80h-FFh)
Return: CF set on error (extensions not supported)
AH = 01h (invalid function)
CF clear if successful
BX = AA55h if installed
AH = major version of extensions
01h = 1.x
20h = 2.0 / EDD-1.0
21h = 2.1 / EDD-1.1
30h = EDD-3.0
AL = internal use
CX = API subset support bitmap (see #00271)
DH = extension version (v2.0+ ??? -- not present in 1.x)
Note: the Phoenix Enhanced Disk Drive Specification v1.0 uses version
2.0 of
the INT 13 Extensions API
SeeAlso: AH=42h"INT 13 Ext",AH=48h"INT 13 Ext"
Bitfields for IBM/MS INT 13 Extensions API support bitmap:
Bit(s) Description (Table 00271)
0 extended disk access functions (AH=42h-44h,47h,48h) supported
1 removable drive controller functions (AH=45h,46h,48h,49h,INT
15/AH=52h)
supported
2 enhanced disk drive (EDD) functions (AH=48h,AH=4Eh) supported
extended drive parameter table is valid (see #00273,#00278)
3-15 reserved (0)
Listing of Error Codes (Referenced from Interrupts Below)
(Table 00234)
Values for disk operation status:
00h successful completion
01h invalid function in AH or invalid parameter
02h address mark not found
03h disk write-protected
04h sector not found/read error
05h reset failed (hard disk)
05h data did not verify correctly (TI Professional PC)
06h disk changed (floppy)
07h drive parameter activity failed (hard disk)
08h DMA overrun
09h data boundary error (attempted DMA across 64K boundary or >80h
sectors)
0Ah bad sector detected (hard disk)
0Bh bad track detected (hard disk)
0Ch unsupported track or invalid media
0Dh invalid number of sectors on format (PS/2 hard disk)
0Eh control data address mark detected (hard disk)
0Fh DMA arbitration level out of range (hard disk)
10h uncorrectable CRC or ECC error on read
11h data ECC corrected (hard disk)
20h controller failure
31h no media in drive (IBM/MS INT 13 extensions)
32h incorrect drive type stored in CMOS (Compaq)
40h seek failed
80h timeout (not ready)
AAh drive not ready (hard disk)
B0h volume not locked in drive (INT 13 extensions)
B1h volume locked in drive (INT 13 extensions)
B2h volume not removable (INT 13 extensions)
B3h volume in use (INT 13 extensions)
B4h lock count exceeded (INT 13 extensions)
B5h valid eject request failed (INT 13 extensions)
BBh undefined error (hard disk)
CCh write fault (hard disk)
E0h status register error (hard disk)
FFh sense operation failed (hard disk)
Interrupt 13h, section AH=08h
--------B-1308-------------------------------
INT 13 - DISK - GET DRIVE PARAMETERS (PC,XT286,CONV,PS,ESDI,SCSI)
AH = 08h
DL = drive (bit 7 set for hard disk)
Return: CF set on error
AH = status (07h) (see #00234)
CF clear if successful
AH = 00h
AL = 00h on at least some BIOSes
BL = drive type (AT/PS2 floppies only) (see #00242)
CH = low eight bits of maximum cylinder number
CL = maximum sector number (bits 5-0)
high two bits of maximum cylinder number (bits
7-6)
DH = maximum head number
DL = number of drives
ES:DI -> drive parameter table (floppies only)
Notes: may return successful even though specified drive is greater than
the
number of attached drives of that type (floppy/hard); check DL to
ensure validity
for systems predating the IBM AT, this call is only valid for hard
disks, as it is implemented by the hard disk BIOS rather than the
ROM BIOS
Toshiba laptops with HardRAM return DL=02h when called with DL=80h,
but fail on DL=81h. The BIOS data at 40h:75h correctly reports 01h.
may indicate only two drives present even if more are attached; to
ensure a correct count, one can use AH=15h to scan through possible
drives
for BIOSes which reserve the last cylinder for testing purposes, the
cylinder count is automatically decremented
on PS/1s with IBM ROM DOS 4, nonexistent drives return CF clear,
BX=CX=0000h, and ES:DI = 0000h:0000h
the PC-Tools PCFORMAT program requires that AL=00h before it will
proceed with the formatting
BUG: several different Compaq BIOSes incorrectly report high-numbered
drives (such as 90h, B0h, D0h, and F0h) as present, giving them the
same geometry as drive 80h; as a workaround, scan through disk
numbers, stopping as soon as the number of valid drives encountered
equals the value in 0040h:0075h
SeeAlso: AH=06h"Adaptec",AH=13h"SyQuest",AH=48h,AH=15h,INT 1E
SeeAlso: INT 41"HARD DISK 0"
(Table 00242)
Values for diskette drive type:
01h 360K
02h 1.2M
03h 720K
04h 1.44M
05h ??? (reportedly an obscure drive type shipped on some IBM machines)
2.88M on some machines (at least AMI 486 BIOS)
06h 2.88M
10h ATAPI Removable Media Device
Interrupt 13h, section AH=48h
--------d-1348-------------------------------
INT 13 - IBM/MS INT 13 Extensions - GET DRIVE PARAMETERS
AH = 48h
DL = drive (80h-FFh)
DS:SI -> buffer for drive parameters (see #00273)
Return: CF clear if successful
AH = 00h
DS:SI buffer filled
CF set on error
AH = error code (see #00234)
BUG: several different Compaq BIOSes incorrectly report high-numbered
drives (such as 90h, B0h, D0h, and F0h) as present, giving them the
same geometry as drive 80h; as a workaround, scan through disk
numbers, stopping as soon as the number of valid drives encountered
equals the value in 0040h:0075h
SeeAlso: AH=08h,AH=41h,AH=49h,MEM 0040h:0075h
Format of IBM/MS INT 13 Extensions drive parameters:
Offset Size Description (Table
00273)
00h WORD (call) size of buffer
(001Ah for v1.x, 001Eh for v2.x, 42h for v3.0)
(ret) size of returned data
02h WORD information flags (see #00274)
04h DWORD number of physical cylinders on drive
08h DWORD number of physical heads on drive
0Ch DWORD number of physical sectors per track
10h QWORD total number of sectors on drive
18h WORD bytes per sector
---v2.0+ ---
1Ah DWORD -> EDD configuration parameters (see
#00278)
FFFFh:FFFFh if not available
---v3.0 ---
1Eh WORD signature BEDDh to indicate presence of
Device Path info
20h BYTE length of Device Path information, including
signature and this
byte (24h for v3.0)
21h 3 BYTEs reserved (0)
24h 4 BYTEs ASCIZ name of host bus ("ISA" or "PCI")
28h 8 BYTEs ASCIZ name of interface type
"ATA"
"ATAPI"
"SCSI"
"USB"
"1394" IEEE 1394 (FireWire)
"FIBRE" Fibre Channel
30h 8 BYTEs Interface Path (see #00275)
38h 8 BYTEs Device Path (see #00276)
40h BYTE reserved (0)
41h BYTE checksum of bytes 1Eh-40h (two's complement
of sum, which makes
the 8-bit sum of bytes 1Eh-41h equal 00h)
Note: if the size is less than 30 on call, the final DWORD will not be
returned by a v2.x implementation; similarly for the Device Path info
SeeAlso: #00277,#03196
Bitfields for IBM/MS INT 13 Extensions information flags:
Bit(s) Description (Table 00274)
0 DMA boundary errors handled transparently
1 cylinder/head/sectors-per-track information is valid
2 removable drive
3 write with verify supported
4 drive has change-line support (required if drive >= 80h is
removable)
5 drive can be locked (required if drive >= 80h is removable)
6 CHS information set to maximum supported values, not current media
15-7 reserved (0)
SeeAlso: #00273
Format of EDD v3.0 Interface Path:
Offset Size Description (Table
00275)
---ISA---
00h WORD 16-bit base address
02h 6 BYTEs reserved (0)
---PCI---
00h BYTE PCI bus number
01h BYTE PCI device number
02h BYTE PCI function number
03h 5 BYTEs reserved (0)
SeeAlso: #00273,#00276
Format of EDD v3.0 Device Path:
Offset Size Description (Table
00276)
---ATA---
00h BYTE flag: 00h = master, 01h = slave
01h 7 BYTEs reserved (0)
---ATAPI---
00h BYTE flag: 00h = master, 01h = slave
01h BYTE logical unit number
02h 6 BYTEs reserved (0)
---SCSI---
00h BYTE logical unit number
01h 7 BYTEs reserved (0)
---USB---
00h BYTE to be determined
01h 7 BYTEs reserved (0)
---IEEE1394---
00h QWORD 64-bit FireWire General Unique Identifier
(GUID)
---FibreChannel---
00h QWORD Word Wide Number (WWN)
SeeAlso: #00273,#00275
Format of Phoenix Enhanced Disk Drive Spec translated drive parameter table:
Offset Size Description (Table
00277)
00h WORD number of cylinders
02h BYTE number of heads
03h BYTE A0h (signature indicating translated table)
04h BYTE number of physical sectors per track
05h WORD starting write precompensation cylinder
number
07h BYTE reserved
08h BYTE control byte (see #03198 at INT 41"DISK
0")
09h WORD number of physical cylinders
0Bh BYTE number of physical heads
0Ch WORD cylinder number of landing zone
0Eh BYTE number of logical sectors per track
0Fh BYTE checksum
Program: the Phoenix Enhanced Disk Drive Specification is an addition to the
IBM/MS INT 13 extensions
SeeAlso: #00278,#03196
Format of Phoenix Enhanced Disk Drive Spec Fixed Disk Parameter Table:
Offset Size Description (Table
00278)
00h WORD physical I/O port base address
02h WORD disk-drive control port address
04h BYTE drive flags (see #00279)
05h BYTE proprietary information
bits 7-4 reserved (0)
bits 3-0: Phoenix proprietary (used by BIOS)
06h BYTE IRQ for drive (bits 3-0; bits 7-4 reserved
and must be 0)
07h BYTE sector count for multi-sector transfers
08h BYTE DMA control
bits 7-4: DMA type (0-2) as per ATA-2
specification
bits 3-0: DMA channel
09h BYTE programmed I/O control
bits 7-4: reserved (0)
bits 3-0: PIO type (1-4) as per ATA-2
specification
0Ah WORD drive options (see #00280)
0Ch 2 BYTEs reserved (0)
0Eh BYTE extension revision level (high nybble=major,
low nybble=minor)
(currently 10h for v1.0 and 11h for v1.1-3.0)
0Fh BYTE 2's complement checksum of bytes 00h-0Eh
8-bit sum of all bytes 00h-0Fh should equal 00h
SeeAlso: #00277
Bitfields for Phoenix Enhanced Disk Drive Spec drive flags:
Bit(s) Description (Table 00279)
7 reserved (1)
6 LBA enabled
5 reserved (1)
4 drive is slave
3-0 reserved (0)
SeeAlso: #00278,#00280
Bitfields for Phoenix Enhanced Disk Drive Spec drive options:
Bit(s) Description (Table 00280)
0 fast PIO enabled
1 fast DMA access enabled
2 block PIO (multi-sector transfers) enabled
3 CHS translation enabled
4 LBA translation enabled
5 removable media
6 ATAPI device (CD-ROM)
7 32-bit transfer mode
---v1.1+ ---
8 ATAPI device uses DRQ to signal readiness for packet command
(must be 0 if bit 6 is 0)
10-9 translation type (must be 00 if bit 3 is 0)
00 Phoenix bit-shifting translation
01 LBA-assisted translation
10 reserved
11 proprietary translation
---v3.0---
11 Ultra DMA access enabled
15-12 reserved
SeeAlso: #00278,#00279
Interrupt 13h, section AH=02h
--------B-1302-------------------------------
INT 13 - DISK - READ SECTOR(S) INTO MEMORY
AH = 02h
AL = number of sectors to read (must be nonzero)
CH = low eight bits of cylinder number
CL = sector number 1-63 (bits 0-5)
high two bits of cylinder (bits 6-7, hard disk only)
DH = head number
DL = drive number (bit 7 set for hard disk)
ES:BX -> data buffer
Return: CF set on error
if AH = 11h (corrected ECC error), AL = burst length
CF clear if successful
AH = status (see #00234)
AL = number of sectors transferred (only valid if CF set for some
BIOSes)
Notes: errors on a floppy may be due to the motor failing to spin up
quickly
enough; the read should be retried at least three times, resetting
the disk with AH=00h between attempts
most BIOSes support "multitrack" reads, where the value in AL
exceeds the number of sectors remaining on the track, in which
case any additional sectors are read beginning at sector 1 on
the following head in the same cylinder; the MSDOS CONFIG.SYS command
MULTITRACK (or the Novell DOS DEBLOCK=) can be used to force DOS to
split disk accesses which would wrap across a track boundary into two
separate calls
the IBM AT BIOS and many other BIOSes use only the low four bits of
DH (head number) since the WD-1003 controller which is the standard
AT controller (and the controller that IDE emulates) only supports
16 heads
AWARD AT BIOS and AMI 386sx BIOS have been extended to handle more
than 1024 cylinders by placing bits 10 and 11 of the cylinder number
into bits 6 and 7 of DH
under Windows95, a volume must be locked (see INT 21/AX=440Dh/CX=084Bh)
in order to perform direct accesses such as INT 13h reads and writes
all versions of MS-DOS (including v7 [Win95]) have a bug which prevents
booting on hard disks with 256 heads, so many modern BIOSes provide
mappings with at most 255 heads
SeeAlso:
AH=03h,AH=0Ah,AH=06h"V10DISK.SYS",AH=21h"PS/1",AH=42h"IBM"
SeeAlso: INT 21/AX=440Dh/CX=084Bh,INT 4D/AH=02h
Interrupt 13h, section AH=42h
--------d-1342-------------------------------
INT 13 - IBM/MS INT 13 Extensions - EXTENDED READ
AH = 42h
DL = drive number
DS:SI -> disk address packet (see #00272)
Return: CF clear if successful
AH = 00h
CF set on error
AH = error code (see #00234)
disk address packet's block count field set to number of blocks
successfully transferred
SeeAlso: AH=02h,AH=41h"INT 13 Ext",AH=43h"INT 13 Ext"
Format of disk address packet:
Offset Size Description (Table
00272)
00h BYTE 10h (size of packet)
01h BYTE reserved (0)
02h WORD number of blocks to transfer (max 007Fh for
Phoenix EDD)
04h DWORD -> transfer buffer
08h QWORD starting absolute block number
(for non-LBA devices, compute as
(Cylinder*NumHeads + SelectedHead) *
SectorPerTrack +
SelectedSector - 1
Interrupt 13h, section AH=03h
--------B-1303-------------------------------
INT 13 - DISK - WRITE DISK SECTOR(S)
AH = 03h
AL = number of sectors to write (must be nonzero)
CH = low eight bits of cylinder number
CL = sector number 1-63 (bits 0-5)
high two bits of cylinder (bits 6-7, hard disk only)
DH = head number
DL = drive number (bit 7 set for hard disk)
ES:BX -> data buffer
Return: CF set on error
CF clear if successful
AH = status (see #00234)
AL = number of sectors transferred
(only valid if CF set for some BIOSes)
Notes: errors on a floppy may be due to the motor failing to spin up
quickly
enough; the write should be retried at least three times, resetting
the disk with AH=00h between attempts
most BIOSes support "multitrack" writes, where the value in
AL
exceeds the number of sectors remaining on the track, in which
case any additional sectors are written beginning at sector 1 on
the following head in the same cylinder; the CONFIG.SYS command
MULTITRACK can be used to force DOS to split disk accesses which
would wrap across a track boundary into two separate calls
the IBM AT BIOS and many other BIOSes use only the low four bits of
DH (head number) since the WD-1003 controller which is the standard
AT controller (and the controller that IDE emulates) only supports
16 heads
AWARD AT BIOS and AMI 386sx BIOS have been extended to handle more
than 1024 cylinders by placing bits 10 and 11 of the cylinder number
into bits 6 and 7 of DH
under Windows95, an application must issue a physical volume lock on
the drive via INT 21/AX=440Dh before it can successfully write to
the disk with this function
SeeAlso:
AH=02h,AH=0Bh,AH=07h"V10DISK.SYS",AH=22h"PS/1",AH=43h"IBM"
SeeAlso: INT 21/AX=440Dh"DOS 3.2+",INT 4D/AH=03h
Interrupt 13h, section AH=43h
--------d-1343-------------------------------
INT 13 - IBM/MS INT 13 Extensions - EXTENDED WRITE
AH = 43h
AL = write flags
---v1.0,2.0---
bit 0: verify write
bits 7-1 reserved (0)
---v2.1+ ---
00h,01h write without verify
02h write with verify
DL = drive number
DS:SI -> disk address packet (see #00272)
Return: CF clear if successful
AH = 00h
CF set on error
AH = error code (see #00234)
disk address packet's block count field set to number of blocks
successfully transferred
Note: the BIOS returns CF set/AH=01h (invalid function) if verify is
requested but not supported
SeeAlso: AH=03h,AH=41h"INT 13 Ext",AH=42h"INT 13 Ext",AH=44h
