More boot sector README updates
This commit is contained in:
Jeff Parsons
Jeff Parsons
parent
6d16f582c7
commit
6d8090649f
3 changed files with 203 additions and 109 deletions
|
|
@ -78,6 +78,41 @@ CHKDSK reports:
|
|||
|
||||
### PC-DOS 1.00 Boot Sector
|
||||
|
||||
The boot sector of the PC-DOS 1.00 disk image contains the following bytes:
|
||||
|
||||
00000000 eb 2f 14 00 00 00 60 00 20 37 2d 4d 61 79 2d 38 |./....`. 7-May-8|
|
||||
00000010 31 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |1...............|
|
||||
00000020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
||||
00000030 00 fa 8c c8 8e d8 ba 00 00 8e d2 bc 00 7c fb a1 |.............|..|
|
||||
00000040 06 7c 8e d8 8e c0 ba 00 00 8b c2 cd 13 72 41 e8 |.|...........rA.|
|
||||
00000050 58 00 72 fb 2e 8b 0e 02 7c 51 bb 00 00 33 d2 b9 |X.r.....|Q...3..|
|
||||
00000060 08 00 be 01 00 56 b0 01 b4 02 cd 13 72 22 5e 58 |.....V......r"^X|
|
||||
00000070 e8 e7 00 2b c6 74 14 fe c5 b1 01 be 08 00 3b c6 |...+.t........;.|
|
||||
00000080 73 04 8b f0 eb 01 96 56 50 eb dd 2e ff 2e 04 7c |s......VP......||
|
||||
00000090 be 44 7d b8 42 7d 50 32 ff ac 24 7f 74 0b 56 b4 |.D}.B}P2..$.t.V.|
|
||||
000000a0 0e bb 07 00 cd 10 5e eb f0 c3 bb 00 00 b9 04 00 |......^.........|
|
||||
000000b0 b8 01 02 cd 13 1e 72 34 8c c8 8e d8 bf 00 00 b9 |......r4........|
|
||||
000000c0 0b 00 26 80 0d 20 26 80 8d 20 00 20 47 e2 f3 bf |..&.. &.. . G...|
|
||||
000000d0 00 00 be 76 7d b9 0b 00 fc f3 a6 75 0f bf 20 00 |...v}......u.. .|
|
||||
000000e0 be 82 7d b9 0b 00 f3 a6 75 02 1f c3 be f9 7c e8 |..}.....u.....|.|
|
||||
000000f0 a5 ff b4 00 cd 16 1f f9 c3 0d 0a 4e 6f 6e 2d 53 |...........Non-S|
|
||||
00000100 79 73 74 65 6d 20 64 69 73 6b 20 6f 72 20 64 69 |ystem disk or di|
|
||||
00000110 73 6b 20 65 72 72 6f f2 0d 0a 52 65 70 6c 61 63 |sk erro...Replac|
|
||||
00000120 65 20 61 6e 64 20 73 74 72 69 6b 65 20 61 6e 79 |e and strike any|
|
||||
00000130 20 6b 65 79 20 77 68 65 6e 20 72 65 61 64 f9 0d | key when read..|
|
||||
00000140 0a 00 cd 18 0d 0a 44 69 73 6b 20 42 6f 6f 74 20 |......Disk Boot |
|
||||
00000150 66 61 69 6c 75 72 e5 0d 0a 00 50 52 8b c6 bf 00 |failur....PR....|
|
||||
00000160 02 f7 e7 03 d8 5a 58 c3 52 6f 62 65 72 74 20 4f |.....ZX.Robert O|
|
||||
00000170 27 52 65 61 72 20 69 62 6d 62 69 6f 20 20 63 6f |'Rear ibmbio co|
|
||||
00000180 6d b0 69 62 6d 64 6f 73 20 20 63 6f 6d b0 c9 00 |m.ibmdos com...|
|
||||
00000190 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
||||
000001a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
||||
000001b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
||||
000001c0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
||||
000001d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
||||
000001e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
||||
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
||||
|
||||
A number of people have already delved into the guts of the PC-DOS 1.00 boot sector, including:
|
||||
|
||||
* [Reverse-Engineering DOS 1.0 – Part 1: The Boot Sector (May 7, 2009 by Michael Steil)](http://www.pagetable.com/?p=165)
|
||||
|
|
@ -265,46 +300,43 @@ Using the PCjs Debugger, we can examine the boot sector in its native environmen
|
|||
&0000:7C00 EB2F JMP 7C31
|
||||
|
||||
>> db 7c00 l200
|
||||
&7C00 EB 2F 14 00 00 00 60 00-20 37 2D 4D 61 79 2D 38 ./....`. 7-May-8
|
||||
&7C10 31 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 1...............
|
||||
&7C20 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&7C30 00 FA 8C C8 8E D8 BA 00-00 8E D2 BC 00 7C FB A1 .............|..
|
||||
&7C40 06 7C 8E D8 8E C0 BA 00-00 8B C2 CD 13 72 41 E8 .|...........rA.
|
||||
&7C50 58 00 72 FB 2E 8B 0E 02-7C 51 BB 00 00 33 D2 B9 X.r.....|Q...3..
|
||||
&7C60 08 00 BE 01 00 56 B0 01-B4 02 CD 13 72 22 5E 58 .....V......r"^X
|
||||
&7C70 E8 E7 00 2B C6 74 14 FE-C5 B1 01 BE 08 00 3B C6 ...+.t........;.
|
||||
&7C80 73 04 8B F0 EB 01 96 56-50 EB DD 2E FF 2E 04 7C s......VP......|
|
||||
&7C90 BE 44 7D B8 42 7D 50 32-FF AC 24 7F 74 0B 56 B4 .D}.B}P2..$t.V.
|
||||
&7CA0 0E BB 07 00 CD 10 5E EB-F0 C3 BB 00 00 B9 04 00 ......^.........
|
||||
&7CB0 B8 01 02 CD 13 1E 72 34-8C C8 8E D8 BF 00 00 B9 ......r4........
|
||||
&7CC0 0B 00 26 80 0D 20 26 80-8D 20 00 20 47 E2 F3 BF ..&.. &.. . G...
|
||||
&7CD0 00 00 BE 76 7D B9 0B 00-FC F3 A6 75 0F BF 20 00 ...v}......u.. .
|
||||
&7CE0 BE 82 7D B9 0B 00 F3 A6-75 02 1F C3 BE F9 7C E8 ..}.....u.....|.
|
||||
&7CF0 A5 FF B4 00 CD 16 1F F9-C3 0D 0A 4E 6F 6E 2D 53 ...........Non-S
|
||||
&7D00 79 73 74 65 6D 20 64 69-73 6B 20 6F 72 20 64 69 ystem disk or di
|
||||
&7D10 73 6B 20 65 72 72 6F F2-0D 0A 52 65 70 6C 61 63 sk erro...Replac
|
||||
&7D20 65 20 61 6E 64 20 73 74-72 69 6B 65 20 61 6E 79 e and strike any
|
||||
&7D30 20 6B 65 79 20 77 68 65-6E 20 72 65 61 64 F9 0D key when read..
|
||||
&7D40 0A 00 CD 18 0D 0A 44 69-73 6B 20 42 6F 6F 74 20 ......Disk Boot
|
||||
&7D50 66 61 69 6C 75 72 E5 0D-0A 00 50 52 8B C6 BF 00 failur....PR....
|
||||
&7D60 02 F7 E7 03 D8 5A 58 C3-52 6F 62 65 72 74 20 4F .....ZX.Robert O
|
||||
&7D70 27 52 65 61 72 20 69 62-6D 62 69 6F 20 20 63 6F 'Rear ibmbio co
|
||||
&7D80 6D B0 69 62 6D 64 6F 73-20 20 63 6F 6D B0 C9 00 m.ibmdos com...
|
||||
&7D90 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&7DA0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&7DB0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&7DC0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&7DD0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&7DE0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&7DF0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&0000:7C00 EB 2F 14 00 00 00 60 00-20 37 2D 00 02 01 01 00 ./....`. 7-.....
|
||||
&0000:7C10 02 40 00 40 01 FE 01 00-08 00 01 00 00 00 00 00 .@.@............
|
||||
&0000:7C20 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&0000:7C30 00 FA 8C C8 8E D8 BA 00-00 8E D2 BC 00 7C FB A1 .............|..
|
||||
&0000:7C40 06 7C 8E D8 8E C0 BA 00-00 8B C2 CD 13 72 41 E8 .|...........rA.
|
||||
&0000:7C50 58 00 72 FB 2E 8B 0E 02-7C 51 BB 00 00 33 D2 B9 X.r.....|Q...3..
|
||||
&0000:7C60 08 00 BE 01 00 56 B0 01-B4 02 CD 13 72 22 5E 58 .....V......r"^X
|
||||
&0000:7C70 E8 E7 00 2B C6 74 14 FE-C5 B1 01 BE 08 00 3B C6 ...+.t........;.
|
||||
&0000:7C80 73 04 8B F0 EB 01 96 56-50 EB DD 2E FF 2E 04 7C s......VP......|
|
||||
&0000:7C90 BE 44 7D B8 42 7D 50 32-FF AC 24 7F 74 0B 56 B4 .D}.B}P2..$t.V.
|
||||
&0000:7CA0 0E BB 07 00 CD 10 5E EB-F0 C3 BB 00 00 B9 04 00 ......^.........
|
||||
&0000:7CB0 B8 01 02 CD 13 1E 72 34-8C C8 8E D8 BF 00 00 B9 ......r4........
|
||||
&0000:7CC0 0B 00 26 80 0D 20 26 80-8D 20 00 20 47 E2 F3 BF ..&.. &.. . G...
|
||||
&0000:7CD0 00 00 BE 76 7D B9 0B 00-FC F3 A6 75 0F BF 20 00 ...v}......u.. .
|
||||
&0000:7CE0 BE 82 7D B9 0B 00 F3 A6-75 02 1F C3 BE F9 7C E8 ..}.....u.....|.
|
||||
&0000:7CF0 A5 FF B4 00 CD 16 1F F9-C3 0D 0A 4E 6F 6E 2D 53 ...........Non-S
|
||||
&0000:7D00 79 73 74 65 6D 20 64 69-73 6B 20 6F 72 20 64 69 ystem disk or di
|
||||
&0000:7D10 73 6B 20 65 72 72 6F F2-0D 0A 52 65 70 6C 61 63 sk erro...Replac
|
||||
&0000:7D20 65 20 61 6E 64 20 73 74-72 69 6B 65 20 61 6E 79 e and strike any
|
||||
&0000:7D30 20 6B 65 79 20 77 68 65-6E 20 72 65 61 64 F9 0D key when read..
|
||||
&0000:7D40 0A 00 CD 18 0D 0A 44 69-73 6B 20 42 6F 6F 74 20 ......Disk Boot
|
||||
&0000:7D50 66 61 69 6C 75 72 E5 0D-0A 00 50 52 8B C6 BF 00 failur....PR....
|
||||
&0000:7D60 02 F7 E7 03 D8 5A 58 C3-52 6F 62 65 72 74 20 4F .....ZX.Robert O
|
||||
&0000:7D70 27 52 65 61 72 20 69 62-6D 62 69 6F 20 20 63 6F 'Rear ibmbio co
|
||||
&0000:7D80 6D B0 69 62 6D 64 6F 73-20 20 63 6F 6D B0 C9 00 m.ibmdos com...
|
||||
&0000:7D90 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&0000:7DA0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&0000:7DB0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&0000:7DC0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&0000:7DD0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&0000:7DE0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
&0000:7DF0 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
|
||||
|
||||
NOTE: When PCjs adds a BPB to the boot sector, the first 32 bytes will actually look like:
|
||||
|
||||
&7C00 EB 2F 14 00 00 00 60 00-20 37 2D 00 02 01 01 00 ./....`. 7-.....
|
||||
&7C10 02 40 00 40 01 FE 01 00-08 00 01 00 00 00 00 00 .@.@............
|
||||
|
||||
The addition of a BPB makes the disk image mountable by modern operating systems and does not
|
||||
otherwise affect the operation of the boot sector or any of the code below.
|
||||
NOTE: PCjs adds a BPB to the boot sector, which is why the first 32 bytes of the boot sector
|
||||
appear slightly different from the original [dump](#pc-dos-100-boot-sector) above. The addition of
|
||||
a BPB makes the disk image mountable by modern operating systems and does not otherwise affect the
|
||||
operation of the boot sector or any of the code below.
|
||||
|
||||
First, let's disassemble the code from `start` (0x7C31):
|
||||
|
||||
|
|
@ -439,6 +471,11 @@ And finally, `IBMBIO_COM` (0x7D76) and `IBMDOS_COM` (0x7D82):
|
|||
&7D78 6D 62 69 6F 20 20 63 6F-6D B0 69 62 6D 64 6F 73 mbio com.ibmdos
|
||||
&7D88 20 20 63 6F 6D B0 C9 00-00 00 00 00 00 00 00 00 com...........
|
||||
|
||||
Interestingly, the [COMPAQ MS-DOS 1.11 Boot Sector](/disks/pcx86/dos/compaq/1.11/#compaq-ms-dos-111-boot-sector)
|
||||
is completely different from all PC-DOS 1.x boot sectors. The COMPAQ boot sector supports both 160Kb and 320Kb
|
||||
formats with less code and without requiring "patches", although that flexibility did require reading the first
|
||||
FAT sector, which PC-DOS 1.x boot sectors did not do.
|
||||
|
||||
### Additional Information From [PC DOS Retro](https://sites.google.com/site/pcdosretro/doshist)
|
||||
|
||||
- distributed on 1 160KB floppy disk
|
||||
|
|
|
|||
Loading…
Reference in a new issue