Int 19

SYSTEM - BOOTSTRAP LOADER

Desc: This interrupt reboots the system without clearing memory or restoring interrupt vectors. Because interrupt vectors are preserved, this interrupt usually causes a system hang if any TSRs have hooked vectors from 00h through 1Ch, particularly INT 08.

Notes: Usually, the BIOS will try to read sector 1, head 0, track 0 from drive

A:
To 0000h:7C00h. If this fails, and a hard disk is installed, the BIOS will read sector 1, head 0, track 0 of the first hard disk. This sector should contain a master bootstrap loader and a partition table (see #00650). After loading the master boot sector at 0000h:7C00h, the master bootstrap loader is given control (see #00653). It will scan the partition table for an active partition, and will then load the operating system's bootstrap loader (contained in the first sector of the active partition) and give it control.. True IBM PCs and most clones issue an INT 18 if neither floppy nor hard disk have a valid boot sector. To accomplish a warm boot equivalent to Ctrl-Alt-Del, store 1234h in 0040h:0072h and jump to FFFFh:0000h. For a cold boot equivalent to a reset, store 0000h at 0040h:0072h before jumping.. VDISK.SYS hooks this interrupt to allow applications to find out how much extended memory has been used by VDISKs (see #00649). DOS 3.3+ PRINT hooks INT 19 but does not set up a correct VDISK header block at the beginning of its INT 19 handler segment, thus causing some programs to overwrite extended memory which is already in use.. The default handler is at F000h:E6F2h for 100% compatible BIOSes. MS-DOS 3.2+ hangs on booting (even from floppy) if the hard disk contains extended partitions which point at each other in a loop, since it will never find the end of the linked list of extended partitions. Under Windows Real and Enhanced modes, calling INT 19 will hang the system in the same was as under bare DOS; under Windows Standard mode, INT 19 will successfully perform a cold reboot as it appears to have been redirected to a MOV AL,0FEh/OUT 64h,AL sequence

BUG: When loading the remainder of the DOS system files fails, various versions of IBMBIO.COM/IO.SYS incorrectly restore INT 1E before calling INT 19, assuming that the boot sector had stored the contents of INT 1E at DS:SI instead of on the stack as it actually does

Format of VDISK header block (at beginning of INT 19 handler's segment): Offset Size Description (Table 00649) 00h 18 BYTEs n/a (for VDISK.SYS, the device driver header) 12h 11 BYTEs signature string "VDISK Vn.m" for VDISK.SYS version n.m 1Dh 15 BYTEs n/a 2Ch 3 BYTEs linear address of first byte of available extended memory

Format of hard disk master boot sector: Offset Size Description (Table 00650) 00h 446 BYTEs Master bootstrap loader code 1BEh 16 BYTEs partition record for partition 1 (see #00651) 1CEh 16 BYTEs partition record for partition 2 1DEh 16 BYTEs partition record for partition 3 1EEh 16 BYTEs partition record for partition 4 1FEh WORD signature, AA55h indicates valid boot block

Format of partition record: Offset Size Description (Table 00651) 00h BYTE boot indicator (80h = active partition) 01h BYTE partition start head 02h BYTE partition start sector (bits 0-5) 03h BYTE partition start track (bits 8,9 in bits 6,7 of sector) 04h BYTE operating system indicator (see #00652) 05h BYTE partition end head 06h BYTE partition end sector (bits 0-5) 07h BYTE partition end track (bits 8,9 in bits 6,7 of sector) 08h DWORD sectors preceding partition 0Ch DWORD length of partition in sectors

See Also: #00650

(Table 00652) Values for operating system indicator: 00h empty partition-table entry 01h DOS 12-bit FAT 02h XENIX root file system 03h XENIX /usr file system (obsolete) 04h DOS 16-bit FAT (up to 32M) 05h DOS 3.3+ extended partition 06h DOS 3.31+ Large File System (16-bit FAT, over 32M) 07h QNX 07h OS/2 HPFS 07h Windows NT NTFS 07h Advanced Unix 07h see partition boot record; could be any of the above or others 08h OS/2 (v1.0-1.3 only) 08h AIX bootable partition, SplitDrive 08h Commodore DOS 08h DELL partition spanning multiple drives 09h AIX data partition 09h Coherent filesystem 0Ah OS/2 Boot Manager 0Ah OPUS 0Ah Coherent swap partition 0Bh Windows95 with 32-bit FAT 0Ch Windows95 with 32-bit FAT (using LBA-mode INT 13 extensions) 0Eh logical-block-addressable VFAT (same as 06h but using LBA-mode INT 13) 0Fh logical-block-addressable VFAT (same as 05h but using LBA-mode INT 13) 10h OPUS 11h OS/2 Boot Manager hidden 12-bit FAT partition 12h Compaq Diagnostics partition 14h (resulted from using Novell DOS 7.0 FDISK to delete Linux Native part) 14h OS/2 Boot Manager hidden sub-32M 16-bit FAT partition 16h OS/2 Boot Manager hidden over-32M 16-bit FAT partition 17h OS/2 Boot Manager hidden HPFS partition 17h hidden NTFS partition 18h AST special Windows swap file ("Zero-Volt Suspend" partition) 19h Willowtech Photon coS 1Bh hidden Windows95 FAT32 partition 1Ch hidden Windows95 FAT32 partition (using LBA-mode INT 13 extensions) 1Eh hidden LBA VFAT partition 20h Willowsoft Overture File System (OFS1) 21h officially listed as reserved 21h FSo2 23h officially listed as reserved 24h NEC MS-DOS 3.x 26h officially listed as reserved 31h officially listed as reserved 33h officially listed as reserved 34h officially listed as reserved 36h officially listed as reserved 38h Theos 3Ch PowerQuest PartitionMagic recovery partition 40h VENIX 80286 41h Personal RISC Boot 41h PowerPC boot partition 42h SFS (Secure File System) by Peter Gutmann 45h EUMEL/Elan 46h EUMEL/Elan 47h EUMEL/Elan 48h EUMEL/Elan 4Fh Oberon boot/data partition 50h OnTrack Disk Manager, read-only partition 51h OnTrack Disk Manager, read/write partition 51h NOVELL 52h CP/M 52h Microport System V/386 53h OnTrack Disk Manager, write-only partition??? 54h OnTrack Disk Manager (DDO) 55h EZ-Drive (see also INT 13/AH=FFh"EZ-Drive") 56h GoldenBow VFeature 5Ch Priam EDISK 61h SpeedStor 63h Unix SysV/386, 386/ix 63h Mach, MtXinu BSD 4.3 on Mach 63h GNU HURD 64h Novell NetWare 286 64h SpeedStore 65h Novell NetWare (3.11) 67h Novell 68h Novell 69h Novell 70h DiskSecure Multi-Boot 71h officially listed as reserved 73h officially listed as reserved 74h officially listed as reserved 75h PC/IX 76h officially listed as reserved 7Eh F.I.X. 80h Minix v1.1 - 1.4a 81h Minix v1.4b+ 81h Linux 81h Mitac Advanced Disk Manager 82h Linux Swap partition 82h Prime 82h Solaris (Unix) 83h Linux native file system (ext2fs/xiafs)

84h OS/2-renumbered type 04h partition (related to hiding DOS C:
Drive) 85h Linux EXT 86h FAT16 volume/stripe set (Windows NT) 87h HPFS Fault-Tolerant mirrored partition 87h NTFS volume/stripe set 93h Amoeba file system 94h Amoeba bad block table 98h Datalight ROM-DOS SuperBoot 99h Mylex EISA SCSI A0h Phoenix NoteBIOS Power Management "Save-to-Disk" partition A1h officially listed as reserved A3h officially listed as reserved A4h officially listed as reserved A5h FreeBSD, BSD/386 A6h OpenBSD A9h NetBSD (http://www.netbsd.org/) B1h officially listed as reserved B3h officially listed as reserved B4h officially listed as reserved B6h officially listed as reserved B6h Windows NT mirror set (master), FAT16 file system B7h BSDI file system (secondarily swap) B7h Windows NT mirror set (master), NTFS file system B8h BSDI swap partition (secondarily file system) BEh Solaris boot partition C0h DR DOS/DR-DOS/Novell DOS secured partition C0h CTOS C1h DR DOS 6.0 LOGIN.EXE-secured 12-bit FAT partition C4h DR DOS 6.0 LOGIN.EXE-secured 16-bit FAT partition C6h DR DOS 6.0 LOGIN.EXE-secured Huge partition C6h corrupted FAT16 volume/stripe set (Windows NT) C6h Windows NT mirror set (slave), FAT16 file system C7h Syrinx Boot C7h corrupted NTFS volume/stripe set C7h Windows NT mirror set (slave), NTFS file system CBh Reserved for DR DOS/DR-DOS/OpenDOS secured FAT32 CCh Reserved for DR DOS/DR-DOS secured FAT32 (LBA) CEh Reserved for DR DOS/DR-DOS secured FAT16 (LBA) D0h Multiuser DOS secured FAT12 D1h Old Multiuser DOS secured FAT12 D4h Old Multiuser DOS secured FAT16 (<= 32M) D5h Old Multiuser DOS secured extended partition D6h Old Multiuser DOS secured FAT16 (> 32M) D8h CP/M-86 DBh CP/M, Concurrent CP/M, Concurrent DOS DBh CTOS (Convergent Technologies OS) E1h SpeedStor 12-bit FAT extended partition E2h DOS read-only (Florian Painke's XFDISK 1.0.4) E3h DOS read-only E3h Storage Dimensions E4h SpeedStor 16-bit FAT extended partition E5h officially listed as reserved E6h officially listed as reserved EBh BeOS BFS (BFS1) F1h Storage Dimensions F2h DOS 3.3+ secondary partition F3h officially listed as reserved F4h SpeedStor F4h Storage Dimensions F5h Prologue F6h officially listed as reserved FEh LANstep FEh IBM PS/2 IML (Initial Microcode Load) partition FFh Xenix bad block table

Note: For partition type 07h, one should inspect the partition boot record for the actual file system type

See Also: #00651



(Table 00653)
Values Bootstrap loader is called with (IBM BIOS):.
CS:IP = 0000h:7C00h.
DH = access
bits 7-6,4-0:
Don't care
bit 5:
=0 device supported by INT 13.
DL = boot drive
00h first floppy
80h first hard disk

Category: Bios - Int 19h - S

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