Emulated ATA-1 controller works with MS-DOS but fails to boot? \ VOGONS

Emulated ATA-1 controller works with MS-DOS but fails to boot?

Topic actions

First post, by superfury

Posted on 2015-09-10, 15:37

superfury Offline

Rank l33t++

Rank: l33t++
Posts: 5843
Joined: 2014-03-08, 11:25
Location: Netherlands

I've written myself an ATA-1 controller I'm using with my emulator:
https://bitbucket.org/superfury/x86emu/src/75 … ide.c?at=master

I can boot from a floppy and format, parition, add files, execute files and read files from it (I'm using the XT-IDE BIOS in 8-bit mode, set by the autodetect).

When I try to boot it(any mounted harddisk), I'm getting an error 80h (after which it tries to boot a floppy which also gives a 80h error resulting in a full reboot of the system). Anyone knows why this happens (It shouldn't timeout according to my logs?)

It's logging:

10:00:10:58.7.0304: Set features:0,0=01
2
30:00:10:58.8.0418: IDENTIFY:0,0=EC
4
50:00:12:90.5.0344: Set features:0,0=01
6
70:00:12:90.6.0139: Set features:0,0=82
8
90:00:12:90.6.0931: SEEK:0,0=70
10
110:00:12:90.6.0933: Seeked!

Edit: While debugging I notice that the hard drive isn't read when executing a hard disk read request (AH=2, DL=0x80). It's firing interupt 13h with AH=02h and DL=02h? It seems to try to load a 'third floppy drive' instead of the hard disk? Anyone knows why this happens?

Author of the UniPCemu emulator.
UniPCemu Git repository
UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io

Reply 1 of 3, by superfury

Posted on 2015-09-10, 19:27

superfury Offline

Rank l33t++

Rank: l33t++
Posts: 5843
Joined: 2014-03-08, 11:25
Location: Netherlands

When backtracing the disassembly given by my emulator I find this:

10:00:14:62.6.0699: C600:0AB7 (B480)MOVB AH, 80
2
30:00:14:62.6.0700: Registers:
4
50:00:14:62.6.0703: AX: A000, BX: 7C00, CX: 0001, DX: 0000
6
70:00:14:62.6.0705: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
8
90:00:14:62.6.0707: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
10
110:00:14:62.6.0709: IP: 0AB7, FLAGS: F246
12
130:00:14:62.6.0714: FLAGSINFO:c1P0a0ZstIdo1111
14
15
16
170:00:14:62.6.0746: Read from memory: 0009FC0D=80 (€)
18
190:00:14:62.6.0750: C600:0AB9 (A00D00)MOVB AL,[DS:000D]
20
210:00:14:62.6.0751: Registers:
22
230:00:14:62.6.0753: AX: 8000, BX: 7C00, CX: 0001, DX: 0000
24
250:00:14:62.6.0756: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
26
270:00:14:62.6.0758: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
28
290:00:14:62.6.0760: IP: 0AB9, FLAGS: F246
30
310:00:14:62.6.0764: FLAGSINFO:c1P0a0ZstIdo1111
32
33
34
350:00:14:62.6.0797: C600:0ABC (84E2)TESTB AH,DL
36
370:00:14:62.6.0799: Registers:
38
390:00:14:62.6.0801: AX: 8080, BX: 7C00, CX: 0001, DX: 0000
40
410:00:14:62.6.0804: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
42
430:00:14:62.6.0806: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
44
450:00:14:62.6.0808: IP: 0ABC, FLAGS: F246
46
470:00:14:62.6.0812: FLAGSINFO:c1P0a0ZstIdo1111
48
49
50
510:00:14:62.6.0866: C600:0ABE (7504)JNZ 0AC4
52
530:00:14:62.6.0868: Registers:
54
550:00:14:62.6.0870: AX: 8080, BX: 7C00, CX: 0001, DX: 0000
56
570:00:14:62.6.0872: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
58
590:00:14:62.6.0875: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
60

…Show last 85 lines

610:00:14:62.6.0877: IP: 0ABE, FLAGS: F246
62
630:00:14:62.6.0881: FLAGSINFO:c1P0a0ZstIdo1111
64
65
66
670:00:14:62.6.0924: Read from memory: 0009FC0C=02 ()
68
690:00:14:62.6.0928: C600:0AC0 (A00C00)MOVB AL,[DS:000C]
70
710:00:14:62.6.0930: Registers:
72
730:00:14:62.6.0932: AX: 8080, BX: 7C00, CX: 0001, DX: 0000
74
750:00:14:62.6.0934: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
76
770:00:14:62.6.0937: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
78
790:00:14:62.6.0939: IP: 0AC0, FLAGS: F246
80
810:00:14:62.6.0943: FLAGSINFO:c1P0a0ZstIdo1111
82
83
84
850:00:14:62.6.0984: C600:0AC3 (98)CBW
86
870:00:14:62.6.0986: Registers:
88
890:00:14:62.6.0988: AX: 8002, BX: 7C00, CX: 0001, DX: 0000
90
910:00:14:62.6.0990: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
92
930:00:14:62.6.0993: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
94
950:00:14:62.6.0994: IP: 0AC3, FLAGS: F246
96
970:00:14:62.6.0999: FLAGSINFO:c1P0a0ZstIdo1111
98
99
100
1010:00:14:62.7.0031: C600:0AC4 (38D4)CMPB AH,DL
102
1030:00:14:62.7.0033: Registers:
104
1050:00:14:62.7.0036: AX: 0002, BX: 7C00, CX: 0001, DX: 0000
106
1070:00:14:62.7.0038: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
108
1090:00:14:62.7.0040: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
110
1110:00:14:62.7.0042: IP: 0AC4, FLAGS: F246
112
1130:00:14:62.7.0046: FLAGSINFO:c1P0a0ZstIdo1111
114
115
116
1170:00:14:62.7.0079: C600:0AC6 (7406)JZ 0ACE
118
1190:00:14:62.7.0081: Registers:
120
1210:00:14:62.7.0083: AX: 0002, BX: 7C00, CX: 0001, DX: 0000
122
1230:00:14:62.7.0085: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
124
1250:00:14:62.7.0088: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
126
1270:00:14:62.7.0089: IP: 0AC6, FLAGS: F246
128
1290:00:14:62.7.0094: FLAGSINFO:c1P0a0ZstIdo1111
130
131
132
1330:00:14:62.7.0126: C600:0ACE (88C2)MOVB DL,AL
134
1350:00:14:62.7.0128: Registers:
136
1370:00:14:62.7.0131: AX: 0002, BX: 7C00, CX: 0001, DX: 0000
138
1390:00:14:62.7.0133: CS: C600, DS: 9FC0, ES: 0000, SS: 0000
140
1410:00:14:62.7.0135: SP: 7ED2, BP: 7ED4, SI: 00F8, DI: 0201
142
1430:00:14:62.7.0137: IP: 0ACE, FLAGS: F246
144
1450:00:14:62.7.0142: FLAGSINFO:c1P0a0ZstIdo1111

So the boot disk to be booted at 0009FC0C is incorrect (it contains 2 instead of 80h). Anyone can tell me why?

Edit: Found the problem: The BIOS detects 4 floppy drives (The BIOS Equipment word has bits 7&6 set to 1, so it detected 4 floppy drives (two times two floppy drives)). Now I just need to find out why the BIOS detects 4 floppy drives instead of 2 (actually installed floppy drives).

Author of the UniPCemu emulator.
UniPCemu Git repository
UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io

Reply 2 of 3, by superfury

Posted on 2015-09-10, 22:09

superfury Offline

Rank l33t++

Rank: l33t++
Posts: 5843
Joined: 2014-03-08, 11:25
Location: Netherlands

I've fixed the problem: The PPI ports 0x62 and 0x63 needed to be added to properly detect the 2 floppy drives (instead of detecting 4 floppy drives and confusing the hard disk BIOS (drives A,B,C,D are floppy, drives E,F,G,H hard disk/cdrom in that case. It tries to boot the C drive (floppy #3) which doesn't exist, so it gives a timeout even through it's supposed to boot the harddisk.

Author of the UniPCemu emulator.
UniPCemu Git repository
UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io

Reply 3 of 3, by superfury

Posted on 2015-09-11, 14:19

superfury Offline

Rank l33t++

Rank: l33t++
Posts: 5843
Joined: 2014-03-08, 11:25
Location: Netherlands

I've just found out another problem: For some reason the BIOS seems to detect 4 floppy drives instead of the 2 floppy drives installed. Anyone knows how the Turbo XT BIOS detects the amount of floppy drives installed (0,1,2,3 or 4 drives)?

Author of the UniPCemu emulator.
UniPCemu Git repository
UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io

Go to top of page Go to top of page

Back to PC Emulation