Can anybody help me get MS-DOS 3.3 booting in my emulator?

Reply 20 of 87, by superfury

Posted on 2015-03-07, 10:19

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The zip file I attached to a few posts back contains the assembly executed up to that point. Looking at the data read, which is supposed to be IO.SYS, I notice, when comparing it to the IO.SYS extracted using Winimage, that it's wrong. So the first sector (19) read is correct (It's the root directory), but the retrieval or calculation of the starting cluster/sector goes wrong? Anyone can see the bug? The root directory is read when Interrupt 13h is called with AX=0201h, at the first time. The first sector of IO.SYS is read to 0000:0700 (ES:BX).

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Reply 21 of 87, by superfury

Posted on 2015-03-07, 11:05

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@SarahWalker: The log is already 3 posts back (The debuggerlog.zip file contains the log). I think that the problem lies in how IO.SYS is loaded: First sector 19 is read, which contains the FAT root directory. Next the first sector containing the contents of IO.SYS is looked up. I think that the calculation of the first sector goes wrong (wrong base?). I know it's somewhere between the first 0000:7D76 and the following address at 0000:7D74, where it's supposed to read the first sector of IO.SYS?

BTW, anyone has the disassembly of the boot sector of MS-DOS 3.3?

It calculated the first sector of IO.SYS to be at:

1Head: 1, Track: 0, Sector: 16. Start sector: 33, Destination: ES:BX=0000:00000700

BTW does anyone have a disassembly of the boot sector, IO.SYS and MSDOS.SYS of MS-DOS 3.3? Just so that I can verify if the disassembly goes wrong (and know what it's doing)?

Or, when possible, a good freeware disassembler for a 8086, which can run on Windows 8.1 64-bit?

Edit: It seems the first 2 sectors of IO.SYS are read correctly. Next some strange data is read:

10:00:17:23.2.0000: Function 02 called.
2
30:00:17:23.6.0000: Read 9/9 sectors from drive 00, start 1. Requested: Head: 0, Track: 0, Sector: 2. Start sector: 1, Destination: ES:BX=0800:00000000

Anyone knows what's it's supposed to read here? The rest of IO.SYS (which shouldn't be there: it points to the start of the FAT, 9 sectors long)?

Or does anyone know a good emulator to compare my assembly output with? In which I can let the boot sector start and compare runtime disassembly with?

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Reply 22 of 87, by Jepael

Posted on 2015-03-09, 08:42

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Two first FAT table entries are reserved and not used as FAT entries. One of the reserved entries contains a "media descriptor byte" or something equivalent and this byte can be used to detect what kind/size flppy there is so it can set the correct parameters to BIOS and actually use the rest of the floppy. Without this the logical parameters of the media is not known (you could have a single-side 40-track floppy in a double-sided 80-track drive)

Reply 23 of 87, by peterferrie

Posted on 2015-03-09, 19:32

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0000:7C9E (03)ADDB AL,BL
This disassembly is improper, based on the affected registers (->ADDB AX,BX).
The debugger log doesn't show the code getting anywhere near where you show the latest problem.
0000:7E48 (8B)MOVW AX,[DS:SI-17FFF]
This disassembly is improper, and the value that is fetched is wrong, too.
As a result, it all goes very wrong.

Reply 24 of 87, by superfury

Posted on 2015-03-10, 14:29

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peterferrie wrote:
0000:7C9E (03)ADDB AL,BL This disassembly is improper, based on the affected registers (->ADDB AX,BX). The debugger log doesn't […]
Show full quote
0000:7C9E (03)ADDB AL,BL
This disassembly is improper, based on the affected registers (->ADDB AX,BX).
The debugger log doesn't show the code getting anywhere near where you show the latest problem.
0000:7E48 (8B)MOVW AX,[DS:SI-17FFF]
This disassembly is improper, and the value that is fetched is wrong, too.
As a result, it all goes very wrong.

You're right. This is (luckily) simply a debugger disassembly done wrong (says ADDW instead of ADDB with 16-bit registers instead of 8-bit now). The instruction is executed as it's supposed now.

The strange value -17FFF was a signed display error: it was using the calculation

1sprintf(result,"-%04X",0xFFFF-unsigned2signed16(displacement));

instead of

1sprintf(result,"-%04X",0-unsigned2signed16(displacement));

, which caused the incorrect disassembly (only disassembly, the normal execution doesn't rely on the sprintf).

So -17FFF=0x8000(unsigned displacement value)=>0-0x8000=-8000, so it's

1MOVW AX,[DS:SI-8000]

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Reply 25 of 87, by peterferrie

Posted on 2015-03-10, 17:40

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Technically, that should still be '+'. However, as I said, the value that is fetched is wrong.
The sequence should be something like 3, 0x40, 5, 0x60, 7, 0x80, etc, not 3, 0. It's a cluster number, so it can't be zero.

Reply 26 of 87, by superfury

Posted on 2015-03-10, 22:56

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How do you mean '+'? The unsigned number 0x8000 equals -32768 when read as a signed value from memory (bit 15 equalling a value of -32768).
So the value is -32768 + value&0x7FFF = -32768 + 0 = -32768, converted to hex -8000. This value is added to the address offset computated, so SI + -8000 = SI-8000, it's substracting from SI, lowering it with 32768.

Here's the new log:

Filename: debuggerlog_20150311_0726.zip
File size: 1.71 MiB
Downloads: 62 downloads
File comment: Most recent debugger log
File license: Fair use/fair dealing exception

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Reply 27 of 87, by peterferrie

Posted on 2015-03-11, 18:06

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Okay, + or - isn't the point here. I'm just referring to Intel documentation.
However...

*The value that is being read is wrong*.
Look in your log for 0000:7e48. You'll find it multiple times, reading the value 0.
It can't be zero ever. It most certainly can't be zero multiple times.
Focus on that part.

Reply 28 of 87, by superfury

Posted on 2015-03-12, 09:46

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This is the first time the read gives invalid information:

10:00:18:02.7.0000: ModR/M address: 0000:FFFF8000=FFFF8000
2
30:00:18:02.8.0000: 0000:7E48 (8B)MOVW AX,[DS:SI-8000]
4
50:00:18:02.8.0000: Registers:
6
70:00:18:02.8.0000: AX: 0000, BX: 0003, CX: 0005, DX: 0000
8
90:00:18:02.8.0000: CS: 0000, DS: 0000, ES: 0070, SS: 0000
10
110:00:18:02.8.0000: SP: 7BDE, BP: 7BE2, SI: 0000, DI: 0000
12
130:00:18:02.8.0000: IP: 7E48, FLAGS: 0246
14
150:00:18:02.9.0000: FLAGSINFO:c1P0a0ZstIdo0000

So the error is somewhere between this point and the previous point (which DO give results)?

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Reply 29 of 87, by peterferrie

Posted on 2015-03-12, 17:44

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The error is most likely that the sector that was read is the wrong one.
I'd check that first.

Reply 30 of 87, by superfury

Posted on 2015-03-12, 18:24

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The location of the previous error is now giving me:

10:00:16:55.3.0999: ModR/M address: 0000:8004=00008004
2
30:00:16:55.3.0999: 0000:7E48 (8B)MOVW AX,[DS:SI-8000]
4
50:00:16:55.3.0999: Registers:
6
70:00:16:55.3.0999: AX: 0004, BX: 0003, CX: 0005, DX: 0000
8
90:00:16:55.3.0999: CS: 0000, DS: 0000, ES: 0070, SS: 0000
10
110:00:16:55.3.0999: SP: 7BDE, BP: 7BE2, SI: 0004, DI: 0000
12
130:00:16:55.5.0000: IP: 7E48, FLAGS: 0203
14
150:00:16:55.5.0000: FLAGSINFO:C1p0a0zstIdo0000
16
17
18
190:00:16:55.6.0999: ModR/M address: 0000:7BF2=00007BF2
20
210:00:16:55.6.0999: 0000:7E4C (F7)TESTW [SS:BP+10],01
22
230:00:16:55.6.0999: Registers:
24
250:00:16:55.6.0999: AX: 0040, BX: 0003, CX: 0005, DX: 0000
26
270:00:16:55.6.0999: CS: 0000, DS: 0000, ES: 0070, SS: 0000
28
290:00:16:55.6.0999: SP: 7BDE, BP: 7BE2, SI: 0004, DI: 0000
30
310:00:16:55.8.0000: IP: 7E4C, FLAGS: 0203
32
330:00:16:55.8.0000: FLAGSINFO:C1p0a0zstIdo0000

Filename: debuggerlog_20150312_1922.zip
File size: 673.33 KiB
Downloads: 67 downloads
File comment: Debugger logs (Both CPU and INT 13h)
File license: Fair use/fair dealing exception

Edit: I'm getting this:

10:00:14:48.4.0000: 0000:7D23 (EA)JMP 0070:0000
2
30:00:14:48.4.0000: Registers:
4
50:00:14:48.4.0000: AX: 0001, BX: 0021, CX: F000, DX: 0100
6
70:00:14:48.4.0000: CS: 0000, DS: 0000, ES: 0000, SS: 0000
8
90:00:14:48.4.0000: SP: 7BF8, BP: 0000, SI: 7DF6, DI: 052B
10
110:00:14:48.4.0000: IP: 7D23, FLAGS: 0206
12
130:00:14:48.4.0000: FLAGSINFO:c1P0a0zstIdo0000
14
15
16
170:00:14:48.7.0000: 0070:0000 (FA)CLI
18
190:00:14:48.7.0000: Registers:
20
210:00:14:48.7.0000: AX: 0001, BX: 0021, CX: F000, DX: 0100
22
230:00:14:48.7.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
24
250:00:14:48.7.0000: SP: 7BF8, BP: 0000, SI: 7DF6, DI: 052B
26
270:00:14:48.7.0000: IP: 0000, FLAGS: 0206
28
290:00:14:48.8.0000: FLAGSINFO:c1P0a0zstIdo0000
30
31
32
330:00:14:49.0.0000: 0070:0001 (33)XORW AX,AX
34
350:00:14:49.0.0000: Registers:
36
370:00:14:49.0.0000: AX: 0001, BX: 0021, CX: F000, DX: 0100
38
390:00:14:49.0.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
40
410:00:14:49.0.0000: SP: 7BF8, BP: 0000, SI: 7DF6, DI: 052B
42
430:00:14:49.0.0000: IP: 0001, FLAGS: 0006
44
450:00:14:49.1.0000: FLAGSINFO:c1P0a0zstido0000
46
47
48
490:00:14:49.3.0000: 0070:0003 (8E)MOVW SS,AX
50
510:00:14:49.3.0000: Registers:
52
530:00:14:49.3.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
54
550:00:14:49.3.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
56
570:00:14:49.3.0000: SP: 7BF8, BP: 0000, SI: 7DF6, DI: 052B
58
590:00:14:49.3.0000: IP: 0003, FLAGS: 0046
60

…Show last 651 lines

610:00:14:49.4.0000: FLAGSINFO:c1P0a0Zstido0000
62
63
64
650:00:14:49.6.0000: 0070:0005 (BC)MOVW SP, 7BE2
66
670:00:14:49.6.0000: Registers:
68
690:00:14:49.6.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
70
710:00:14:49.6.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
72
730:00:14:49.6.0000: SP: 7BF8, BP: 0000, SI: 7DF6, DI: 052B
74
750:00:14:49.7.0000: IP: 0005, FLAGS: 0046
76
770:00:14:49.7.0000: FLAGSINFO:c1P0a0Zstido0000
78
79
80
810:00:14:49.9.0000: 0070:0008 (BD)MOVW BP, 7BE2
82
830:00:14:49.9.0000: Registers:
84
850:00:14:49.9.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
86
870:00:14:49.9.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
88
890:00:14:49.9.0000: SP: 7BE2, BP: 0000, SI: 7DF6, DI: 052B
90
910:00:14:49.9.0000: IP: 0008, FLAGS: 0046
92
930:00:14:50.0.0000: FLAGSINFO:c1P0a0Zstido0000
94
95
96
970:00:14:50.2.0000: 0070:000B (FB)STI
98
990:00:14:50.2.0000: Registers:
100
1010:00:14:50.2.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
102
1030:00:14:50.2.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
104
1050:00:14:50.2.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
106
1070:00:14:50.2.0000: IP: 000B, FLAGS: 0046
108
1090:00:14:50.2.0000: FLAGSINFO:c1P0a0Zstido0000
110
111
112
1130:00:14:50.5.0000: ModR/M address: 0000:7BF6=00007BF6
114
1150:00:14:51.2.0000: 0070:000C (89)MOVW [SS:BP+14],BX
116
1170:00:14:51.2.0000: Registers:
118
1190:00:14:51.2.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
120
1210:00:14:51.2.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
122
1230:00:14:51.2.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
124
1250:00:14:51.3.0000: IP: 000C, FLAGS: 0246
126
1270:00:14:51.3.0000: FLAGSINFO:c1P0a0ZstIdo0000
128
129
130
1310:00:14:51.5.0000: ModR/M address: 0000:7BFC=00007BFC
132
1330:00:14:51.5.0000: 0070:000F (88)MOVB [SS:BP+1A],CH
134
1350:00:14:51.5.0000: Registers:
136
1370:00:14:51.5.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
138
1390:00:14:51.5.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
140
1410:00:14:51.5.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
142
1430:00:14:51.6.0000: IP: 000F, FLAGS: 0246
144
1450:00:14:51.6.0000: FLAGSINFO:c1P0a0ZstIdo0000
146
147
148
1490:00:14:51.8.0000: ModR/M address: 0000:7BFA=00007BFA
150
1510:00:14:52.1.0000: 0070:0012 (88)MOVB [SS:BP+18],DL
152
1530:00:14:52.1.0000: Registers:
154
1550:00:14:52.1.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
156
1570:00:14:52.1.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
158
1590:00:14:52.2.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
160
1610:00:14:52.2.0000: IP: 0012, FLAGS: 0246
162
1630:00:14:52.2.0000: FLAGSINFO:c1P0a0ZstIdo0000
164
165
166
1670:00:14:52.4.0000: 0070:0015 (33)XORW AX,AX
168
1690:00:14:52.4.0000: Registers:
170
1710:00:14:52.4.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
172
1730:00:14:52.4.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
174
1750:00:14:52.4.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
176
1770:00:14:52.5.0000: IP: 0015, FLAGS: 0246
178
1790:00:14:52.5.0000: FLAGSINFO:c1P0a0ZstIdo0000
180
181
182
1830:00:14:52.7.0000: 0070:0017 (8E)MOVW DS,AX
184
1850:00:14:52.7.0000: Registers:
186
1870:00:14:52.7.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
188
1890:00:14:52.7.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
190
1910:00:14:52.7.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
192
1930:00:14:52.7.0000: IP: 0017, FLAGS: 0246
194
1950:00:14:52.8.0000: FLAGSINFO:c1P0a0ZstIdo0000
196
197
198
1990:00:14:53.0.0000: 0070:0019 (A1)MOVW AX,[DS:7C18]
200
2010:00:14:53.0.0000: Registers:
202
2030:00:14:53.0.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
204
2050:00:14:53.0.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
206
2070:00:14:53.0.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
208
2090:00:14:53.0.0000: IP: 0019, FLAGS: 0246
210
2110:00:14:53.1.0000: FLAGSINFO:c1P0a0ZstIdo0000
212
213
214
2150:00:14:53.3.0000: ModR/M address: 0000:7BF8=00007BF8
216
2170:00:14:53.3.0000: 0070:001C (89)MOVW [SS:BP+16],AX
218
2190:00:14:53.3.0000: Registers:
220
2210:00:14:53.3.0000: AX: 0012, BX: 0021, CX: F000, DX: 0100
222
2230:00:14:53.3.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
224
2250:00:14:53.4.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
226
2270:00:14:53.4.0000: IP: 001C, FLAGS: 0246
228
2290:00:14:53.4.0000: FLAGSINFO:c1P0a0ZstIdo0000
230
231
232
2330:00:14:53.6.0000: 0070:001F (A1)MOVW AX,[DS:7C1A]
234
2350:00:14:53.6.0000: Registers:
236
2370:00:14:53.6.0000: AX: 0012, BX: 0021, CX: F000, DX: 0100
238
2390:00:14:53.6.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
240
2410:00:14:53.6.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
242
2430:00:14:53.7.0000: IP: 001F, FLAGS: 0246
244
2450:00:14:53.7.0000: FLAGSINFO:c1P0a0ZstIdo0000
246
247
248
2490:00:14:53.9.0000: ModR/M address: 0000:7BE2=00007BE2
250
2510:00:14:53.9.0000: 0070:0022 (89)MOVW [SS:BP+00],AX
252
2530:00:14:53.9.0000: Registers:
254
2550:00:14:53.9.0000: AX: 0002, BX: 0021, CX: F000, DX: 0100
256
2570:00:14:53.9.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
258
2590:00:14:53.9.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
260
2610:00:14:54.0.0000: IP: 0022, FLAGS: 0246
262
2630:00:14:54.0.0000: FLAGSINFO:c1P0a0ZstIdo0000
264
265
266
2670:00:14:54.2.0000: 0070:0025 (A1)MOVW AX,[DS:7C16]
268
2690:00:14:54.2.0000: Registers:
270
2710:00:14:54.2.0000: AX: 0002, BX: 0021, CX: F000, DX: 0100
272
2730:00:14:54.2.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
274
2750:00:14:54.2.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
276
2770:00:14:54.3.0000: IP: 0025, FLAGS: 0246
278
2790:00:14:54.3.0000: FLAGSINFO:c1P0a0ZstIdo0000
280
281
282
2830:00:14:54.5.0000: ModR/M address: 0000:7BEA=00007BEA
284
2850:00:14:54.5.0000: 0070:0028 (89)MOVW [SS:BP+08],AX
286
2870:00:14:54.5.0000: Registers:
288
2890:00:14:54.5.0000: AX: 0009, BX: 0021, CX: F000, DX: 0100
290
2910:00:14:54.5.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
292
2930:00:14:54.5.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
294
2950:00:14:54.6.0000: IP: 0028, FLAGS: 0246
296
2970:00:14:54.6.0000: FLAGSINFO:c1P0a0ZstIdo0000
298
299
300
3010:00:14:54.8.0000: 0070:002B (A1)MOVW AX,[DS:7C1C]
302
3030:00:14:54.8.0000: Registers:
304
3050:00:14:54.8.0000: AX: 0009, BX: 0021, CX: F000, DX: 0100
306
3070:00:14:54.8.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
308
3090:00:14:54.8.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
310
3110:00:14:54.8.0000: IP: 002B, FLAGS: 0246
312
3130:00:14:54.9.0000: FLAGSINFO:c1P0a0ZstIdo0000
314
315
316
3170:00:14:55.1.0000: ModR/M address: 0000:7BEC=00007BEC
318
3190:00:14:55.1.0000: 0070:002E (89)MOVW [SS:BP+0A],AX
320
3210:00:14:55.1.0000: Registers:
322
3230:00:14:55.1.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
324
3250:00:14:55.1.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
326
3270:00:14:55.1.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
328
3290:00:14:55.2.0000: IP: 002E, FLAGS: 0246
330
3310:00:14:55.2.0000: FLAGSINFO:c1P0a0ZstIdo0000
332
333
334
3350:00:14:55.4.0000: 0070:0031 (A1)MOVW AX,[DS:7C0E]
336
3370:00:14:55.4.0000: Registers:
338
3390:00:14:55.4.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
340
3410:00:14:55.4.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
342
3430:00:14:55.4.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
344
3450:00:14:55.5.0000: IP: 0031, FLAGS: 0246
346
3470:00:14:55.5.0000: FLAGSINFO:c1P0a0ZstIdo0000
348
349
350
3510:00:14:55.8.0000: ModR/M address: 0000:7BF0=00007BF0
352
3530:00:14:55.8.0000: 0070:0034 (89)MOVW [SS:BP+0E],AX
354
3550:00:14:55.8.0000: Registers:
356
3570:00:14:55.8.0000: AX: 0001, BX: 0021, CX: F000, DX: 0100
358
3590:00:14:55.8.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
360
3610:00:14:55.8.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
362
3630:00:14:55.9.0000: IP: 0034, FLAGS: 0246
364
3650:00:14:55.9.0000: FLAGSINFO:c1P0a0ZstIdo0000
366
367
368
3690:00:14:56.1.0000: 0070:0037 (A1)MOVW AX,[DS:7C0B]
370
3710:00:14:56.1.0000: Registers:
372
3730:00:14:56.1.0000: AX: 0001, BX: 0021, CX: F000, DX: 0100
374
3750:00:14:56.1.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
376
3770:00:14:56.1.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
378
3790:00:14:56.1.0000: IP: 0037, FLAGS: 0246
380
3810:00:14:56.2.0000: FLAGSINFO:c1P0a0ZstIdo0000
382
383
384
3850:00:14:56.4.0000: ModR/M address: 0000:7BEE=00007BEE
386
3870:00:14:56.4.0000: 0070:003A (89)MOVW [SS:BP+0C],AX
388
3890:00:14:56.4.0000: Registers:
390
3910:00:14:56.4.0000: AX: 0200, BX: 0021, CX: F000, DX: 0100
392
3930:00:14:56.4.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
394
3950:00:14:56.4.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
396
3970:00:14:56.5.0000: IP: 003A, FLAGS: 0246
398
3990:00:14:56.5.0000: FLAGSINFO:c1P0a0ZstIdo0000
400
401
402
4030:00:14:56.7.0000: 0070:003D (33)XORW AX,AX
404
4050:00:14:56.7.0000: Registers:
406
4070:00:14:56.7.0000: AX: 0200, BX: 0021, CX: F000, DX: 0100
408
4090:00:14:56.7.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
410
4110:00:14:56.7.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
412
4130:00:14:56.7.0000: IP: 003D, FLAGS: 0246
414
4150:00:14:56.8.0000: FLAGSINFO:c1P0a0ZstIdo0000
416
417
418
4190:00:14:57.0.0000: 0070:003F (8E)MOVW DS,AX
420
4210:00:14:57.0.0000: Registers:
422
4230:00:14:57.0.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
424
4250:00:14:57.0.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
426
4270:00:14:57.0.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
428
4290:00:14:57.0.0000: IP: 003F, FLAGS: 0246
430
4310:00:14:57.1.0000: FLAGSINFO:c1P0a0ZstIdo0000
432
433
434
4350:00:14:57.3.0000: 0070:0041 (A1)MOVW AX,[DS:7C0B]
436
4370:00:14:57.3.0000: Registers:
438
4390:00:14:57.3.0000: AX: 0000, BX: 0021, CX: F000, DX: 0100
440
4410:00:14:57.3.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
442
4430:00:14:57.3.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
444
4450:00:14:57.3.0000: IP: 0041, FLAGS: 0246
446
4470:00:14:57.4.0000: FLAGSINFO:c1P0a0ZstIdo0000
448
449
450
4510:00:14:57.6.0000: 0070:0044 (33)XORW BX,BX
452
4530:00:14:57.6.0000: Registers:
454
4550:00:14:57.6.0000: AX: 0200, BX: 0021, CX: F000, DX: 0100
456
4570:00:14:57.6.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
458
4590:00:14:57.6.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
460
4610:00:14:57.6.0000: IP: 0044, FLAGS: 0246
462
4630:00:14:57.7.0000: FLAGSINFO:c1P0a0ZstIdo0000
464
465
466
4670:00:14:57.9.0000: ModR/M address: 0000:7C0D=00007C0D
468
4690:00:14:57.9.0000: 0070:0046 (8A)MOVB BL,[DS:7C0D]
470
4710:00:14:57.9.0000: Registers:
472
4730:00:14:57.9.0000: AX: 0200, BX: 0000, CX: F000, DX: 0100
474
4750:00:14:57.9.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
476
4770:00:14:57.9.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
478
4790:00:14:58.0.0000: IP: 0046, FLAGS: 0246
480
4810:00:14:58.0.0000: FLAGSINFO:c1P0a0ZstIdo0000
482
483
484
4850:00:14:58.2.0000: 0070:004A (F7)MULW BX
486
4870:00:14:58.2.0000: Registers:
488
4890:00:14:58.2.0000: AX: 0200, BX: 0001, CX: F000, DX: 0100
490
4910:00:14:58.2.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
492
4930:00:14:58.2.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
494
4950:00:14:58.2.0000: IP: 004A, FLAGS: 0246
496
4970:00:14:58.3.0000: FLAGSINFO:c1P0a0ZstIdo0000
498
499
500
5010:00:14:58.5.0000: ModR/M address: 0000:7BE4=00007BE4
502
5030:00:14:58.5.0000: 0070:004C (89)MOVW [SS:BP+02],AX
504
5050:00:14:58.5.0000: Registers:
506
5070:00:14:58.5.0000: AX: 0200, BX: 0001, CX: F000, DX: 0000
508
5090:00:14:58.5.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
510
5110:00:14:58.5.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
512
5130:00:14:58.6.0000: IP: 004C, FLAGS: 0206
514
5150:00:14:58.6.0000: FLAGSINFO:c1P0a0zstIdo0000
516
517
518
5190:00:14:58.8.0000: ModR/M address: 0000:7BFB=00007BFB
520
5210:00:14:58.8.0000: 0070:004F (C6)MOVB [SS:BP+19],01
522
5230:00:14:58.8.0000: Registers:
524
5250:00:14:58.8.0000: AX: 0200, BX: 0001, CX: F000, DX: 0000
526
5270:00:14:58.8.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
528
5290:00:14:58.8.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
530
5310:00:14:58.9.0000: IP: 004F, FLAGS: 0206
532
5330:00:14:58.9.0000: FLAGSINFO:c1P0a0zstIdo0000
534
535
536
5370:00:14:59.1.0000: ModR/M address: 0000:7BFC=00007BFC
538
5390:00:14:59.1.0000: 0070:0053 (80)CMPB [SS:BP+1A],F8
540
5410:00:14:59.1.0000: Registers:
542
5430:00:14:59.1.0000: AX: 0200, BX: 0001, CX: F000, DX: 0000
544
5450:00:14:59.1.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
546
5470:00:14:59.1.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
548
5490:00:14:59.2.0000: IP: 0053, FLAGS: 0206
550
5510:00:14:59.2.0000: FLAGSINFO:c1P0a0zstIdo0000
552
553
554
5550:00:14:59.4.0000: 0070:0057 (75)JNZ 0082
556
5570:00:14:59.4.0000: Registers:
558
5590:00:14:59.4.0000: AX: 0200, BX: 0001, CX: F000, DX: 0000
560
5610:00:14:59.5.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
562
5630:00:14:59.5.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
564
5650:00:14:59.5.0000: IP: 0057, FLAGS: 0293
566
5670:00:14:59.5.0000: FLAGSINFO:C1p0A0zStIdo0000
568
569
570
5710:00:14:59.7.0000: 0070:0082 (0E)PUSH CS
572
5730:00:14:59.7.0000: Registers:
574
5750:00:14:59.7.0000: AX: 0200, BX: 0001, CX: F000, DX: 0000
576
5770:00:14:59.7.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
578
5790:00:14:59.7.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
580
5810:00:14:59.7.0000: IP: 0082, FLAGS: 0293
582
5830:00:14:59.7.0000: FLAGSINFO:C1p0A0zStIdo0000
584
585
586
5870:00:14:60.0.0000: 0070:0083 (1F)POP DS
588
5890:00:14:60.0.0000: Registers:
590
5910:00:14:60.0.0000: AX: 0200, BX: 0001, CX: F000, DX: 0000
592
5930:00:14:60.0.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
594
5950:00:14:60.0.0000: SP: 7BE0, BP: 7BE2, SI: 7DF6, DI: 052B
596
5970:00:14:60.1.0000: IP: 0083, FLAGS: 0293
598
5990:00:14:60.1.0000: FLAGSINFO:C1p0A0zStIdo0000
600
601
602
6030:00:14:60.3.0000: 0070:0084 (33)XORW AX,AX
604
6050:00:14:60.3.0000: Registers:
606
6070:00:14:60.3.0000: AX: 0200, BX: 0001, CX: F000, DX: 0000
608
6090:00:14:60.3.0000: CS: 0070, DS: 0070, ES: 0000, SS: 0000
610
6110:00:14:60.3.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
612
6130:00:14:60.3.0000: IP: 0084, FLAGS: 0293
614
6150:00:14:60.3.0000: FLAGSINFO:C1p0A0zStIdo0000
616
617
618
6190:00:14:60.6.0000: 0070:0086 (8E)MOVW ES,AX
620
6210:00:14:60.6.0000: Registers:
622
6230:00:14:60.6.0000: AX: 0000, BX: 0001, CX: F000, DX: 0000
624
6250:00:14:60.6.0000: CS: 0070, DS: 0070, ES: 0000, SS: 0000
626
6270:00:14:60.6.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
628
6290:00:14:60.6.0000: IP: 0086, FLAGS: 0256
630
6310:00:14:60.7.0000: FLAGSINFO:c1P0A0ZstIdo0000
632
633
634
6350:00:14:60.9.0000: 0070:0088 (BE)MOVW SI, 0099
636
6370:00:14:60.9.0000: Registers:
638
6390:00:14:60.9.0000: AX: 0000, BX: 0001, CX: F000, DX: 0000
640
6410:00:14:60.9.0000: CS: 0070, DS: 0070, ES: 0000, SS: 0000
642
6430:00:14:60.9.0000: SP: 7BE2, BP: 7BE2, SI: 7DF6, DI: 052B
644
6450:00:14:60.9.0000: IP: 0088, FLAGS: 0256
646
6470:00:14:61.0.0000: FLAGSINFO:c1P0A0ZstIdo0000
648
649
650
6510:00:14:61.2.0000: 0070:008B (BF)MOVW DI, 7D00
652
6530:00:14:61.2.0000: Registers:
654
6550:00:14:61.2.0000: AX: 0000, BX: 0001, CX: F000, DX: 0000
656
6570:00:14:61.2.0000: CS: 0070, DS: 0070, ES: 0000, SS: 0000
658
6590:00:14:61.2.0000: SP: 7BE2, BP: 7BE2, SI: 0099, DI: 052B
660
6610:00:14:61.2.0000: IP: 008B, FLAGS: 0256
662
6630:00:14:61.2.0000: FLAGSINFO:c1P0A0ZstIdo0000
664
665
666
6670:00:14:61.5.0000: 0070:008E (B9)MOVW CX, 0175
668
6690:00:14:61.5.0000: Registers:
670
6710:00:14:61.5.0000: AX: 0000, BX: 0001, CX: F000, DX: 0000
672
6730:00:14:61.5.0000: CS: 0070, DS: 0070, ES: 0000, SS: 0000
674
6750:00:14:61.5.0000: SP: 7BE2, BP: 7BE2, SI: 0099, DI: 7D00
676
6770:00:14:61.5.0000: IP: 008E, FLAGS: 0256
678
6790:00:14:61.5.0000: FLAGSINFO:c1P0A0ZstIdo0000
680
681
682
6830:00:14:61.8.0000: 0070:0091 (90)NOP
684
6850:00:14:61.8.0000: Registers:
686
6870:00:14:61.8.0000: AX: 0000, BX: 0001, CX: 0175, DX: 0000
688
6890:00:14:61.8.0000: CS: 0070, DS: 0070, ES: 0000, SS: 0000
690
6910:00:14:61.8.0000: SP: 7BE2, BP: 7BE2, SI: 0099, DI: 7D00
692
6930:00:14:61.8.0000: IP: 0091, FLAGS: 0256
694
6950:00:14:61.8.0000: FLAGSINFO:c1P0A0ZstIdo0000
696
697
698
6990:00:14:62.1.0000: 0070:0092 (A4)REP MOVSB
700
7010:00:14:62.1.0000: Registers:
702
7030:00:14:62.1.0000: AX: 0000, BX: 0001, CX: 0175, DX: 0000
704
7050:00:14:62.1.0000: CS: 0070, DS: 0070, ES: 0000, SS: 0000
706
7070:00:14:62.1.0000: SP: 7BE2, BP: 7BE2, SI: 0099, DI: 7D00
708
7090:00:14:62.1.0000: IP: 0092, FLAGS: 0256
710
7110:00:14:62.1.0000: FLAGSINFO:c1P0A0ZstIdo0000

I guess this means IO.SYS is loaded correctly this time (at 0070:0000)?

But, looking at my int13.log, it seems it keeps loading blocks at the same location (ES:BX 0070:0000) after sector 33 (which is the first sector of IO.SYS)?

Looking at the contents loaded, up to sector 83, it's the rest of IO.SYS (sector 83 contains the last part of IO.SYS). But why does it keep loading parts of itself at 0070:0000 (ES:BX)?

It maybe an error in opcode 01? The data at the address isn't being increased:

10:00:16:23.1.0000: ModR/M address: 0000:7BF4=00007BF4
2
30:00:16:23.1.0000: 0000:7D5C (01)ADDW [SS:BP+12],AX
4
50:00:16:23.1.0000: Registers:
6
70:00:16:23.1.0000: AX: 0200, BX: 0000, CX: 0005, DX: 0000
8
90:00:16:23.1.0000: CS: 0000, DS: 0000, ES: 0070, SS: 0000
10
110:00:16:23.1.0000: SP: 7BE0, BP: 7BE2, SI: 0001, DI: 0000
12
130:00:16:23.2.0000: IP: 7D5C, FLAGS: 0206
14
150:00:16:23.2.0000: FLAGSINFO:c1P0a0zstIdo0000

Edit: I've found out that all 16-bit moves from register to memory (which uses my self-written procedure) used a 8-bit write to MODR/M instead of 16-bit. This caused only the low byte (which is always 0) to be written as 0, thus having no effect on increasing the location for the next cluster.

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

Reply 31 of 87, by superfury

Posted on 2015-03-12, 19:27

superfury Online

Rank l33t++

Rank: l33t++
Posts: 5459
Joined: 2014-03-08, 11:25
Location: Netherlands

I'm now getting a:

1NEC IO.SYS for MS-DOS(R)  Version 3.30
2Copyright (C) 1988 NEC Corporation
3Copyright (C) 1981-1987 Microsoft Corporation

This text is blinking.

Then it's doing nothing anymore (no disk I/O).

Looking at the disassembly log:

10:02:10:06.6.0000: 0070:4125 (B9)MOVW CX, 4000
2
30:02:10:06.6.0000: Registers:
4
50:02:10:06.6.0000: AX: 0200, BX: 078C, CX: 0000, DX: 0000
6
70:02:10:06.6.0000: CS: 0070, DS: 0690, ES: 0070, SS: 0000
8
90:02:10:06.6.0000: SP: 06F4, BP: 0001, SI: 0070, DI: 052D
10
110:02:10:06.6.0000: IP: 4125, FLAGS: 0203
12
130:02:10:06.7.0000: FLAGSINFO:C1p0a0zstIdo0000
14
15
16
170:02:10:06.8.0999: 0070:4128 (E2)LOOP 4128
18
190:02:10:06.8.0999: Registers:
20
210:02:10:06.8.0999: AX: 0200, BX: 078C, CX: 4000, DX: 0000
22
230:02:10:06.8.0999: CS: 0070, DS: 0690, ES: 0070, SS: 0000
24
250:02:10:06.8.0999: SP: 06F4, BP: 0001, SI: 0070, DI: 052D
26
270:02:10:07.0.0000: IP: 4128, FLAGS: 0203
28
290:02:10:07.0.0000: FLAGSINFO:C1p0a0zstIdo0000

So this keeps looping until CX=0.

Finally it gets to ADDB.

10:03:02:30.5.0000: 0070:36D5 (B2)MOVB DL, 80
2
30:03:02:30.5.0000: Registers:
4
50:03:02:30.5.0000: AX: 0004, BX: 078C, CX: 0000, DX: 048D
6
70:03:02:30.5.0000: CS: 0070, DS: 0690, ES: 0070, SS: 0000
8
90:03:02:30.5.0000: SP: 0700, BP: 7BE2, SI: 1E80, DI: 1E7C
10
110:03:02:30.6.0000: IP: 36D5, FLAGS: 0206
12
130:03:02:30.6.0000: FLAGSINFO:c1P0a0zstIdo0000
14
15
16
170:03:02:30.8.0000: 0070:36D7 (B4)MOVB AH, 08
18
190:03:02:30.8.0000: Registers:
20
210:03:02:30.8.0000: AX: 0004, BX: 078C, CX: 0000, DX: 0480
22
230:03:02:30.8.0000: CS: 0070, DS: 0690, ES: 0070, SS: 0000
24
250:03:02:30.8.0000: SP: 0700, BP: 7BE2, SI: 1E80, DI: 1E7C
26
270:03:02:30.9.0000: IP: 36D7, FLAGS: 0206
28
290:03:02:30.9.0000: FLAGSINFO:c1P0a0zstIdo0000
30
31
32
330:03:02:31.1.0000: 0070:36D9 (CD)INT 13
34
350:03:02:31.1.0000: Registers:
36
370:03:02:31.1.0000: AX: 0804, BX: 078C, CX: 0000, DX: 0480
38
390:03:02:31.1.0000: CS: 0070, DS: 0690, ES: 0070, SS: 0000
40
410:03:02:31.1.0000: SP: 0700, BP: 7BE2, SI: 1E80, DI: 1E7C
42
430:03:02:31.2.0000: IP: 36D9, FLAGS: 0206
44
450:03:02:31.2.0000: FLAGSINFO:c1P0a0zstIdo0000

After this it just gets:

10:03:02:31.4.0000: ModR/M address: 0690:260C=00008F0C
2
30:03:02:31.4.0000: F000:0FB5 (00)ADDB [DS:BX+SI],AL
4
50:03:02:31.4.0000: Registers:
6
70:03:02:31.4.0000: AX: 0804, BX: 078C, CX: 0000, DX: 0480
8
90:03:02:31.4.0000: CS: F000, DS: 0690, ES: 0070, SS: 0000
10
110:03:02:31.4.0000: SP: 06FA, BP: 7BE2, SI: 1E80, DI: 1E7C
12
130:03:02:31.5.0000: IP: 0FB5, FLAGS: 0006
14
150:03:02:31.5.0000: FLAGSINFO:c1P0a0zstido0000

So there's just 0 bytes I think.

Attachments

Filename

debuggerlog_20150312_2038.zip

File size

1.58 MiB

Downloads

63 downloads

File comment

Debugger disassembly log and INT 13h log

File license

Fair use/fair dealing exception

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

Reply 32 of 87, by superfury

Posted on 2015-03-13, 08:24

superfury Online

Rank l33t++

Rank: l33t++
Posts: 5459
Joined: 2014-03-08, 11:25
Location: Netherlands

I think I've found the problem:

10:02:04:79.5.0000: ModR/M address: 0000:004C=0000004C
2
30:02:04:79.5.0000: 0070:34E3 (C7064C00B50F)MOVW [DS:004C],0fb5
4
50:02:04:79.5.0000: Registers:
6
70:02:04:79.5.0000: AX: F000, BX: 0021, CX: F000, DX: 0000
8
90:02:04:79.5.0000: CS: 0070, DS: 0000, ES: 0070, SS: 0000
10
110:02:04:79.5.0000: SP: 7BE0, BP: 7BE2, SI: 74E2, DI: 72D4
12
130:02:04:79.6.0000: IP: 34E3, FLAGS: 0056
14
150:02:04:79.6.0000: FLAGSINFO:c1P0A0Zstido0000

This overwrites my BIOS INT13 handler's offset with something of MS-DOS? Is this instruction supposed to happen? Is the segment supposed to be adjusted too? Or is this a decoding error?

I've also adjusted the debugger and MMU to generate a full log of the read opcode data. (instead of just giving the execution byte of the opcode, it now gives the entire instruction that was decoded by the CPU, for finding errors in CPU decoding or simply for completeness of the debugger (like Turbo Debugger used to do))

Filename: debugger_20150313_0917.zip
File size: 2.27 MiB
Downloads: 63 downloads
File comment: Debugger log.
File license: Fair use/fair dealing exception

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

Reply 33 of 87, by SarahWalker

Posted on 2015-03-13, 08:35

SarahWalker Offline

Rank Member

Rank: Member
Posts: 262
Joined: 2007-08-19, 10:51

The instruction immediately following is interpreted wrong :

10:02:04:79.5.0000: ModR/M address: 0000:004C=0000004C
20:02:04:79.5.0000: 0070:34E3 (C7064C00B50F)MOVW [DS:004C],0fb5
30:02:04:79.5.0000: Registers:
40:02:04:79.5.0000: AX: F000, BX: 0021, CX: F000, DX: 0000
50:02:04:79.5.0000: CS: 0070, DS: 0000, ES: 0070, SS: 0000
60:02:04:79.5.0000: SP: 7BE0, BP: 7BE2, SI: 74E2, DI: 72D4
70:02:04:79.6.0000: IP: 34E3, FLAGS: 0056
80:02:04:79.6.0000: FLAGSINFO:c1P0A0Zstido0000
9
100:02:04:79.8.0000: 0070:34E9 (8C0E)MOVW SI,CS
110:02:04:79.8.0000: Registers:
120:02:04:79.8.0000: AX: F000, BX: 0021, CX: F000, DX: 0000
130:02:04:79.8.0000: CS: 0070, DS: 0000, ES: 0070, SS: 0000
140:02:04:79.8.0000: SP: 7BE0, BP: 7BE2, SI: 74E2, DI: 72D4
150:02:04:79.8.0000: IP: 34E9, FLAGS: 0056
160:02:04:79.9.0000: FLAGSINFO:c1P0A0Zstido0000

8C0E4E00 is MOV [DS:004E], CS

Reply 34 of 87, by superfury

Posted on 2015-03-13, 09:13

superfury Online

Rank l33t++

Rank: l33t++
Posts: 5459
Joined: 2014-03-08, 11:25
Location: Netherlands

Fixed that little bug. It now gives a MOV [DS:004E],CS instruction (there were some errors in ModR/M decoding).

Now, according to my INT13 log, it seems to be getting into an infinite loop:

10:06:12:63.0.0000: Function 02 called.
2
30:06:12:63.0.0000: Read 1/1 sectors from drive 00, start 34. Requested: Head: 1, Track: 0, Sector: 17. Start sector: 34, Destination: ES:BX=0690:00004000
4
50:06:14:08.2.0000: Function 02 called.
6
70:06:14:08.2.0000: Read 1/1 sectors from drive 00, start 734. Requested: Head: 0, Track: 20, Sector: 15. Start sector: 734, Destination: ES:BX=0690:00004600
8
90:06:15:01.7.0000: Function 02 called.
10
110:06:15:01.7.0000: Read 1/1 sectors from drive 00, start 1278. Requested: Head: 1, Track: 35, Sector: 1. Start sector: 1278, Destination: ES:BX=0690:00004800
12
130:06:15:82.1.0000: Function 02 called.
14
150:06:15:82.1.0000: Read 1/1 sectors from drive 00, start 1720. Requested: Head: 1, Track: 47, Sector: 11. Start sector: 1720, Destination: ES:BX=0690:00004A00
16
170:06:16:82.6.0000: Function 02 called.
18
190:06:16:82.6.0000: Read 1/1 sectors from drive 00, start 1781. Requested: Head: 0, Track: 49, Sector: 18. Start sector: 1781, Destination: ES:BX=0690:00004C00

This keeps repeating (infinitely?) on and on with increasing BX values (start location increased every sector read).

Filename: debuggerlog_20150313_1011.zip
File size: 4.62 MiB
Downloads: 63 downloads
File comment: Debugger log with opcode 8C bugfix.
File license: Fair use/fair dealing exception

Is it expecting something after this location:

10:03:14:06.7.0000: 0070:0F57 (CD13)INT 13
2
30:03:14:06.7.0000: Registers:
4
50:03:14:06.7.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
6
70:03:14:06.7.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
8
90:03:14:06.7.0000: SP: 06EA, BP: 0005, SI: 0522, DI: 0482
10
110:03:14:06.8.0000: IP: 0F57, FLAGS: 0046
12
130:03:14:06.8.0000: FLAGSINFO:c1P0a0Zstido0000

Is this my error?

10:03:14:07.0.0000: 0070:0FB5 (2EA3C000)MOVW [CS:00C0],AX
2
30:03:14:07.0.0000: Registers:
4
50:03:14:07.0.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
6
70:03:14:07.0.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
8
90:03:14:07.0.0000: SP: 06E4, BP: 0005, SI: 0522, DI: 0482
10
110:03:14:07.1.0000: IP: 0FB5, FLAGS: 0046
12
130:03:14:07.1.0000: FLAGSINFO:c1P0a0Zstido0000
14
15
16
170:03:14:07.3.0000: 0070:0FB9 (9C)PUSHF
18
190:03:14:07.3.0000: Registers:
20
210:03:14:07.3.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
22
230:03:14:07.3.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
24
250:03:14:07.3.0000: SP: 06E4, BP: 0005, SI: 0522, DI: 0482
26
270:03:14:07.3.0000: IP: 0FB9, FLAGS: 0046
28
290:03:14:07.4.0000: FLAGSINFO:c1P0a0Zstido0000
30
31
32
330:03:14:07.6.0000: 0070:0FBA (80FC05)CMPB AH,05
34
350:03:14:07.6.0000: Registers:
36
370:03:14:07.6.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
38
390:03:14:07.6.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
40
410:03:14:07.6.0000: SP: 06E2, BP: 0005, SI: 0522, DI: 0482
42
430:03:14:07.7.0000: IP: 0FBA, FLAGS: 0046
44
450:03:14:07.7.0000: FLAGSINFO:c1P0a0Zstido0000
46
47
48
490:03:14:07.9.0000: 0070:0FBD (750A)JNZ 0FC9
50
510:03:14:07.9.0000: Registers:
52
530:03:14:07.9.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
54
550:03:14:07.9.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
56
570:03:14:07.9.0000: SP: 06E2, BP: 0005, SI: 0522, DI: 0482
58
590:03:14:08.0.0000: IP: 0FBD, FLAGS: 0093
60

…Show last 117 lines

610:03:14:08.0.0000: FLAGSINFO:C1p0A0zStido0000
62
63
64
650:03:14:08.2.0000: 0070:0FC9 (80FC08)CMPB AH,08
66
670:03:14:08.2.0000: Registers:
68
690:03:14:08.2.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
70
710:03:14:08.2.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
72
730:03:14:08.3.0000: SP: 06E2, BP: 0005, SI: 0522, DI: 0482
74
750:03:14:08.3.0000: IP: 0FC9, FLAGS: 0093
76
770:03:14:08.3.0000: FLAGSINFO:C1p0A0zStido0000
78
79
80
810:03:14:08.5.0000: 0070:0FCC (7412)JZ 0FE0
82
830:03:14:08.5.0000: Registers:
84
850:03:14:08.5.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
86
870:03:14:08.5.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
88
890:03:14:08.5.0000: SP: 06E2, BP: 0005, SI: 0522, DI: 0482
90
910:03:14:08.5.0000: IP: 0FCC, FLAGS: 0097
92
930:03:14:08.6.0000: FLAGSINFO:C1P0A0zStido0000
94
95
96
970:03:14:08.8.0000: 0070:0FCE (80FC15)CMPB AH,15
98
990:03:14:08.8.0000: Registers:
100
1010:03:14:08.8.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
102
1030:03:14:08.8.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
104
1050:03:14:08.8.0000: SP: 06E2, BP: 0005, SI: 0522, DI: 0482
106
1070:03:14:08.8.0000: IP: 0FCE, FLAGS: 0097
108
1090:03:14:08.9.0000: FLAGSINFO:C1P0A0zStido0000
110
111
112
1130:03:14:09.1.0000: 0070:0FD1 (740D)JZ 0FE0
114
1150:03:14:09.1.0000: Registers:
116
1170:03:14:09.1.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
118
1190:03:14:09.1.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
120
1210:03:14:09.1.0000: SP: 06E2, BP: 0005, SI: 0522, DI: 0482
122
1230:03:14:09.1.0000: IP: 0FD1, FLAGS: 0097
124
1250:03:14:09.2.0000: FLAGSINFO:C1P0A0zStido0000
126
127
128
1290:03:14:09.4.0000: ModR/M address: 0070:00B4=000007B4
130
1310:03:14:09.4.0000: 0070:0FD3 (2EFF1EB400)CALL [CS:00B4]
132
1330:03:14:09.4.0000: Registers:
134
1350:03:14:09.4.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
136
1370:03:14:09.4.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000
138
1390:03:14:09.4.0000: SP: 06E2, BP: 0005, SI: 0522, DI: 0482
140
1410:03:14:09.5.0000: IP: 0FD3, FLAGS: 0097
142
1430:03:14:09.5.0000: FLAGSINFO:C1P0A0zStido0000
144
145
146
1470:03:14:09.7.0000: ModR/M address: 0070:2122=00002822
148
1490:03:14:09.7.0000: F000:00E0 (FE380700)<INTERNAL CALLBACK> 0007
150
1510:03:14:09.7.0000: Registers:
152
1530:03:14:09.7.0000: AX: 0201, BX: 1C00, CX: 3112, DX: 0000
154
1550:03:14:09.7.0000: CS: F000, DS: 0070, ES: 0690, SS: 0000
156
1570:03:14:09.8.0000: SP: 06DE, BP: 0005, SI: 0522, DI: 0482
158
1590:03:14:09.8.0000: IP: 00E0, FLAGS: 0097
160
1610:03:14:09.8.0000: FLAGSINFO:C1P0A0zStido0000
162
163
164
1650:03:14:10.0.0000: F000:00E4 (CF)IRET
166
1670:03:14:10.0.0000: Registers:
168
1690:03:14:10.1.0000: AX: 0001, BX: 1C00, CX: 3112, DX: 0000
170
1710:03:14:10.1.0000: CS: F000, DS: 0070, ES: 0690, SS: 0000
172
1730:03:14:10.1.0000: SP: 06DE, BP: 0005, SI: 0522, DI: 0482
174
1750:03:14:10.1.0000: IP: 00E4, FLAGS: 0097
176
1770:03:14:10.1.0000: FLAGSINFO:C1P0A0zStido0000

What's at address 0000:07B4 in memory?

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

Reply 35 of 87, by peterferrie

Posted on 2015-03-13, 17:15

peterferrie Offline

Rank Oldbie

Rank: Oldbie
Posts: 649
Joined: 2008-05-08, 21:54

Start here:

0:02:04:50.4.0000: 0070:3534 (2E891E7833)MOVW [CS:3378],BX
0:02:04:50.4.0000: AX: 0000, BX: 0021, CX: F002, DX: 0000
0:02:04:50.4.0000: CS: 0070, DS: 0000, ES: 0070, SS: 0000

note the values in CS (70) and BX (21). Then we reach

0:03:04:48.6.0000: 0070:3F30 (03067833)ADDW AX,[DS:3378]
0:03:04:48.6.0000: AX: 0033, BX: 0035, CX: 0001, DX: 0000
0:03:04:48.6.0000: CS: 0070, DS: 0070, ES: 0690, SS: 0000

note the value in DS (70) and see what happens next:

0:03:04:48.9.0000: 0070:3F34 (8BD0)MOVW DX,AX
0:03:04:48.9.0000: AX: 0033, BX: 0035, CX: 0001, DX: 0000

DS:3378 is apparently zero, despite the write above.

Reply 36 of 87, by superfury

Posted on 2015-03-14, 15:36

superfury Online

Rank l33t++

Rank: l33t++
Posts: 5459
Joined: 2014-03-08, 11:25
Location: Netherlands

Some INT13 call is overwriting a lot of memory in the range that value is saved:

10:10:29:40.6.0000: Written to memory: 000006F0=46
2
30:10:29:40.7.0000: Written to memory: 000006F1=00
4
50:10:29:40.7.0000: Written to memory: 000006EE=70
6
70:10:29:40.8.0000: Written to memory: 000006EF=00
8
90:10:29:40.8.0000: Written to memory: 000006EC=59
10
110:10:29:40.9.0000: Written to memory: 000006ED=0F
12
130:10:29:40.9.0000: 0070:0F57 (CD13)INT 13
14
150:10:29:41.0.0000: Registers:
16
170:10:29:41.0.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
18
190:10:29:41.1.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
20
210:10:29:41.1.0000: SP: 06F2, BP: 0005, SI: 0522, DI: 0482
22
230:10:29:41.2.0000: IP: 0F57, FLAGS: 0046
24
250:10:29:41.2.0000: FLAGSINFO:c1P0a0Zstido0000
26
27
28
290:10:29:41.3.0000: Written to memory: 000007C0=09
30
310:10:29:41.3.0000: Written to memory: 000007C1=02
32
330:10:29:41.4.0000: 0070:0FB5 (2EA3C000)MOVW [CS:00C0],AX
34
350:10:29:41.4.0000: Registers:
36
370:10:29:41.5.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
38
390:10:29:41.5.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
40
410:10:29:41.6.0000: SP: 06EC, BP: 0005, SI: 0522, DI: 0482
42
430:10:29:41.6.0000: IP: 0FB5, FLAGS: 0046
44
450:10:29:41.7.0000: FLAGSINFO:c1P0a0Zstido0000
46
47
48
490:10:29:41.8.0000: Written to memory: 000006EA=46
50
510:10:29:41.8.0000: Written to memory: 000006EB=00
52
530:10:29:41.9.0000: 0070:0FB9 (9C)PUSHF
54
550:10:29:41.9.0000: Registers:
56
570:10:29:41.9.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
58
590:10:29:42.0.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
60

…Show last 151 lines

610:10:29:42.0.0000: SP: 06EC, BP: 0005, SI: 0522, DI: 0482
62
630:10:29:42.1.0000: IP: 0FB9, FLAGS: 0046
64
650:10:29:42.1.0000: FLAGSINFO:c1P0a0Zstido0000
66
67
68
690:10:29:42.2.0000: 0070:0FBA (80FC05)CMPB AH,05
70
710:10:29:42.3.0000: Registers:
72
730:10:29:42.3.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
74
750:10:29:42.4.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
76
770:10:29:42.4.0000: SP: 06EA, BP: 0005, SI: 0522, DI: 0482
78
790:10:29:42.5.0000: IP: 0FBA, FLAGS: 0046
80
810:10:29:42.5.0000: FLAGSINFO:c1P0a0Zstido0000
82
83
84
850:10:29:42.6.0000: 0070:0FBD (750A)JNZ 0FC9
86
870:10:29:42.6.0000: Registers:
88
890:10:29:42.7.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
90
910:10:29:42.7.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
92
930:10:29:42.8.0000: SP: 06EA, BP: 0005, SI: 0522, DI: 0482
94
950:10:29:42.8.0000: IP: 0FBD, FLAGS: 0093
96
970:10:29:42.9.0000: FLAGSINFO:C1p0A0zStido0000
98
99
100
1010:10:29:43.0.0000: 0070:0FC9 (80FC08)CMPB AH,08
102
1030:10:29:43.0.0000: Registers:
104
1050:10:29:43.1.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
106
1070:10:29:43.1.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
108
1090:10:29:43.2.0000: SP: 06EA, BP: 0005, SI: 0522, DI: 0482
110
1110:10:29:43.2.0000: IP: 0FC9, FLAGS: 0093
112
1130:10:29:43.2.0000: FLAGSINFO:C1p0A0zStido0000
114
115
116
1170:10:29:43.3.0000: 0070:0FCC (7412)JZ 0FE0
118
1190:10:29:43.4.0000: Registers:
120
1210:10:29:43.4.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
122
1230:10:29:43.5.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
124
1250:10:29:43.5.0000: SP: 06EA, BP: 0005, SI: 0522, DI: 0482
126
1270:10:29:43.6.0000: IP: 0FCC, FLAGS: 0097
128
1290:10:29:43.6.0000: FLAGSINFO:C1P0A0zStido0000
130
131
132
1330:10:29:43.7.0000: 0070:0FCE (80FC15)CMPB AH,15
134
1350:10:29:43.8.0000: Registers:
136
1370:10:29:43.8.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
138
1390:10:29:43.9.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
140
1410:10:29:43.9.0000: SP: 06EA, BP: 0005, SI: 0522, DI: 0482
142
1430:10:29:43.9.0000: IP: 0FCE, FLAGS: 0097
144
1450:10:29:44.0.0000: FLAGSINFO:C1P0A0zStido0000
146
147
148
1490:10:29:44.1.0000: 0070:0FD1 (740D)JZ 0FE0
150
1510:10:29:44.1.0000: Registers:
152
1530:10:29:44.2.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
154
1550:10:29:44.2.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
156
1570:10:29:44.3.0000: SP: 06EA, BP: 0005, SI: 0522, DI: 0482
158
1590:10:29:44.3.0000: IP: 0FD1, FLAGS: 0097
160
1610:10:29:44.4.0000: FLAGSINFO:C1P0A0zStido0000
162
163
164
1650:10:29:44.4.0000: Written to memory: 000006E8=70
166
1670:10:29:44.5.0000: Written to memory: 000006E9=00
168
1690:10:29:44.5.0000: Written to memory: 000006E6=D8
170
1710:10:29:44.6.0000: Written to memory: 000006E7=0F
172
1730:10:29:44.6.0000: ModR/M address: 0070:00B4=000007B4
174
1750:10:29:44.7.0000: 0070:0FD3 (2EFF1EB400)CALL [CS:00B4]
176
1770:10:29:44.7.0000: Registers:
178
1790:10:29:44.8.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
180
1810:10:29:44.8.0000: CS: 0070, DS: 0070, ES: 02A0, SS: 0000
182
1830:10:29:44.9.0000: SP: 06EA, BP: 0005, SI: 0522, DI: 0482
184
1850:10:29:44.9.0000: IP: 0FD3, FLAGS: 0097
186
1870:10:29:45.0.0000: FLAGSINFO:C1P0A0zStido0000
188
189
190
1910:10:29:45.1.0000: Written to memory: 000006E4=00
192
1930:10:29:45.1.0000: Written to memory: 000006E5=F0
194
1950:10:29:45.2.0000: Written to memory: 000006E2=E5
196
1970:10:29:45.2.0000: Written to memory: 000006E3=00
198
1990:10:29:45.3.0000: F000:00E0 (9AE60000F0)CALL f000:00e6
200
2010:10:29:45.3.0000: Registers:
202
2030:10:29:45.4.0000: AX: 0209, BX: 0000, CX: 0002, DX: 0000
204
2050:10:29:45.4.0000: CS: F000, DS: 0070, ES: 02A0, SS: 0000
206
2070:10:29:45.4.0000: SP: 06E6, BP: 0005, SI: 0522, DI: 0482
208
2090:10:29:45.5.0000: IP: 00E0, FLAGS: 0097
210
2110:10:29:45.5.0000: FLAGSINFO:C1P0A0zStido0000

(lots of memory is overwritten by this INT13 call (reading 9 sectors)), clearing the value that was stored at 0070:3378 by reading 9 sectors to 02A0:0000 up to 02A0:2DA2.

Filename: debuggerlog_20150314_1634.zip
File size: 2.12 MiB
Downloads: 70 downloads
File comment: Debugger log with memory writes logged (including internal interrupt calls).
File license: Fair use/fair dealing exception

This seems to load the value into ES:

10:10:28:23.4.0000: 0070:3A19 (A17F33)MOVW AX,[DS:337F]
2
30:10:28:23.5.0000: Registers:
4
50:10:28:23.5.0000: AX: F009, BX: 0100, CX: 0009, DX: 0001
6
70:10:28:23.5.0000: CS: 0070, DS: 0070, ES: 0070, SS: 0000
8
90:10:28:23.6.0000: SP: 06FE, BP: 7BE2, SI: 0001, DI: 0000
10
110:10:28:23.6.0000: IP: 3A19, FLAGS: 0056
12
130:10:28:23.7.0000: FLAGSINFO:c1P0A0Zstido0000
14
15
16
170:10:28:23.8.0000: 0070:3A1C (8EC0)MOVW ES,AX
18
190:10:28:23.8.0000: Registers:
20
210:10:28:23.9.0000: AX: 02A0, BX: 0100, CX: 0009, DX: 0001
22
230:10:28:23.9.0000: CS: 0070, DS: 0070, ES: 0070, SS: 0000
24
250:10:28:24.0.0000: SP: 06FE, BP: 7BE2, SI: 0001, DI: 0000
26
270:10:28:24.0.0000: IP: 3A1C, FLAGS: 0056
28
290:10:28:24.1.0000: FLAGSINFO:c1P0A0Zstido0000
30

Edit: This seems to be loaded at:

10:07:20:76.1.0000: 0070:362C (A10B7C)MOVW AX,[DS:7C0B]
2
30:07:20:76.2.0000: Registers:
4
50:07:20:76.3.0000: AX: 03C0, BX: 078C, CX: F000, DX: 0009
6
70:07:20:76.3.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
8
90:07:20:76.3.0000: SP: 06F8, BP: 7BE2, SI: 7C36, DI: 052D
10
110:07:20:76.4.0000: IP: 362C, FLAGS: 0246
12
130:07:20:76.4.0000: FLAGSINFO:c1P0a0ZstIdo0000
14
15
16
170:07:20:76.5.0000: 0070:362F (B109)MOVB CL, 09
18
190:07:20:76.6.0000: Registers:
20
210:07:20:76.6.0000: AX: 0200, BX: 078C, CX: F000, DX: 0009
22
230:07:20:76.7.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
24
250:07:20:76.8.0000: SP: 06F8, BP: 7BE2, SI: 7C36, DI: 052D
26
270:07:20:76.8.0000: IP: 362F, FLAGS: 0246
28
290:07:20:76.8.0000: FLAGSINFO:c1P0a0ZstIdo0000
30
31
32
330:07:20:76.9.0000: 0070:3631 (D3E8)SHRW AX,CL
34
350:07:20:77.0.0000: Registers:
36
370:07:20:77.0.0000: AX: 0200, BX: 078C, CX: F009, DX: 0009
38
390:07:20:77.1.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
40
410:07:20:77.1.0000: SP: 06F8, BP: 7BE2, SI: 7C36, DI: 052D
42
430:07:20:77.2.0000: IP: 3631, FLAGS: 0246
44
450:07:20:77.2.0000: FLAGSINFO:c1P0a0ZstIdo0000
46
47
48
490:07:20:77.3.0000: 0070:3633 (59)POP CX
50
510:07:20:77.4.0000: Registers:
52
530:07:20:77.4.0000: AX: 0001, BX: 078C, CX: F009, DX: 0009
54
550:07:20:77.5.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
56
570:07:20:77.5.0000: SP: 06F8, BP: 7BE2, SI: 7C36, DI: 052D
58
590:07:20:77.6.0000: IP: 3633, FLAGS: 0202
60

…Show last 167 lines

610:07:20:77.6.0000: FLAGSINFO:c1p0a0zstIdo0000
62
63
64
650:07:20:77.7.0000: 0070:3634 (F7E2)MULW DX
66
670:07:20:77.8.0000: Registers:
68
690:07:20:77.8.0000: AX: 0001, BX: 078C, CX: F000, DX: 0009
70
710:07:20:77.9.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
72
730:07:20:77.9.0000: SP: 06FA, BP: 7BE2, SI: 7C36, DI: 052D
74
750:07:20:78.0.0000: IP: 3634, FLAGS: 0202
76
770:07:20:78.0.0000: FLAGSINFO:c1p0a0zstIdo0000
78
79
80
810:07:20:78.1.0000: 0070:3636 (8BD0)MOVW DX,AX
82
830:07:20:78.2.0000: Registers:
84
850:07:20:78.2.0000: AX: 0009, BX: 078C, CX: F000, DX: 0000
86
870:07:20:78.2.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
88
890:07:20:78.3.0000: SP: 06FA, BP: 7BE2, SI: 7C36, DI: 052D
90
910:07:20:78.3.0000: IP: 3636, FLAGS: 0206
92
930:07:20:78.4.0000: FLAGSINFO:c1P0a0zstIdo0000
94
95
96
970:07:20:78.5.0000: 0070:3638 (D1E2)SHLW DX,1
98
990:07:20:78.5.0000: Registers:
100
1010:07:20:78.5.0000: AX: 0009, BX: 078C, CX: F000, DX: 0009
102
1030:07:20:78.6.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
104
1050:07:20:78.6.0000: SP: 06FA, BP: 7BE2, SI: 7C36, DI: 052D
106
1070:07:20:78.7.0000: IP: 3638, FLAGS: 0206
108
1090:07:20:78.8.0000: FLAGSINFO:c1P0a0zstIdo0000
110
111
112
1130:07:20:78.9.0000: 0070:363A (D1E2)SHLW DX,1
114
1150:07:20:78.9.0000: Registers:
116
1170:07:20:78.9.0000: AX: 0009, BX: 078C, CX: F000, DX: 0012
118
1190:07:20:79.0.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
120
1210:07:20:79.1.0000: SP: 06FA, BP: 7BE2, SI: 7C36, DI: 052D
122
1230:07:20:79.1.0000: IP: 363A, FLAGS: 0206
124
1250:07:20:79.2.0000: FLAGSINFO:c1P0a0zstIdo0000
126
127
128
1290:07:20:79.3.0000: 0070:363C (D1E2)SHLW DX,1
130
1310:07:20:79.3.0000: Registers:
132
1330:07:20:79.3.0000: AX: 0009, BX: 078C, CX: F000, DX: 0024
134
1350:07:20:79.4.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
136
1370:07:20:79.4.0000: SP: 06FA, BP: 7BE2, SI: 7C36, DI: 052D
138
1390:07:20:79.5.0000: IP: 363C, FLAGS: 0206
140
1410:07:20:79.5.0000: FLAGSINFO:c1P0a0zstIdo0000
142
143
144
1450:07:20:79.6.0000: 0070:363E (D1E2)SHLW DX,1
146
1470:07:20:79.6.0000: Registers:
148
1490:07:20:79.7.0000: AX: 0009, BX: 078C, CX: F000, DX: 0048
150
1510:07:20:79.8.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
152
1530:07:20:79.8.0000: SP: 06FA, BP: 7BE2, SI: 7C36, DI: 052D
154
1550:07:20:79.8.0000: IP: 363E, FLAGS: 0206
156
1570:07:20:79.9.0000: FLAGSINFO:c1P0a0zstIdo0000
158
159
160
1610:07:20:80.0.0000: 0070:3640 (D1E2)SHLW DX,1
162
1630:07:20:80.0.0000: Registers:
164
1650:07:20:80.0.0000: AX: 0009, BX: 078C, CX: F000, DX: 0090
166
1670:07:20:80.1.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
168
1690:07:20:80.1.0000: SP: 06FA, BP: 7BE2, SI: 7C36, DI: 052D
170
1710:07:20:80.2.0000: IP: 3640, FLAGS: 0206
172
1730:07:20:80.2.0000: FLAGSINFO:c1P0a0zstIdo0000
174
175
176
1770:07:20:80.3.0000: 0070:3642 (58)POP AX
178
1790:07:20:80.3.0000: Registers:
180
1810:07:20:80.4.0000: AX: 0009, BX: 078C, CX: F000, DX: 0120
182
1830:07:20:80.4.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
184
1850:07:20:80.4.0000: SP: 06FA, BP: 7BE2, SI: 7C36, DI: 052D
186
1870:07:20:80.5.0000: IP: 3642, FLAGS: 0202
188
1890:07:20:80.5.0000: FLAGSINFO:c1p0a0zstIdo0000
190
191
192
1930:07:20:80.6.0000: 0070:3643 (2BC2)SUBW AX,DX
194
1950:07:20:80.6.0000: Registers:
196
1970:07:20:80.7.0000: AX: 03C0, BX: 078C, CX: F000, DX: 0120
198
1990:07:20:80.7.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
200
2010:07:20:80.9.0000: SP: 06FC, BP: 7BE2, SI: 7C36, DI: 052D
202
2030:07:20:80.9.0000: IP: 3643, FLAGS: 0202
204
2050:07:20:81.0.0000: FLAGSINFO:c1p0a0zstIdo0000
206
207
208
2090:07:20:81.1.0000: Written to memory: 00003A7F=A0
210
2110:07:20:81.1.0000: Written to memory: 00003A80=02
212
2130:07:20:81.2.0000: 0070:3645 (2EA37F33)MOVW [CS:337F],AX
214
2150:07:20:81.2.0000: Registers:
216
2170:07:20:81.3.0000: AX: 02A0, BX: 078C, CX: F000, DX: 0120
218
2190:07:20:81.4.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
220
2210:07:20:81.5.0000: SP: 06FC, BP: 7BE2, SI: 7C36, DI: 052D
222
2230:07:20:81.5.0000: IP: 3645, FLAGS: 0206
224
2250:07:20:81.6.0000: FLAGSINFO:c1P0a0zstIdo0000
226

This seems to be based at:

10:07:20:76.1.0000: 0070:362C (A10B7C)MOVW AX,[DS:7C0B]
2
30:07:20:76.2.0000: Registers:
4
50:07:20:76.3.0000: AX: 03C0, BX: 078C, CX: F000, DX: 0009
6
70:07:20:76.3.0000: CS: 0070, DS: 0000, ES: 0000, SS: 0000
8
90:07:20:76.3.0000: SP: 06F8, BP: 7BE2, SI: 7C36, DI: 052D
10
110:07:20:76.4.0000: IP: 362C, FLAGS: 0246
12
130:07:20:76.4.0000: FLAGSINFO:c1P0a0ZstIdo0000
14

0000:7C0B seems to contain the sector size (512 bytes).

Is this correct?

So it decodes to the following formula:

1destination segment = ((Sector size(512)>>9)*9)
2destination segment -= (destination segment<<5)
3
4destination of the load is destination segment:0000

Is this the correct formula for determining the segment?

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UniPCemu Git repository
UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io

Reply 37 of 87, by peterferrie

Posted on 2015-03-15, 05:29

peterferrie Offline

Rank Oldbie

Rank: Oldbie
Posts: 649
Joined: 2008-05-08, 21:54

I'll have to investigate later what you're seeing. However, if you see reads to segment 0x70 while running from segment 0x70, then that's your problem.
These are the reads that you should see:
9ea0:0 (9 sectors)
690:0 (6)
690:c00 (0x12)
690:3000 (0x12)
690:5400 (0x11)
986:10 (1)
b72:10 (1)
b72:10 (1)
b51:10 (1)
c8b:0 (1)
c8b:200 (0x12)
c8b:2600 (0x12)
c8b:4a00 (0x0c)
b30:10 (1)

Reply 38 of 87, by crazyc

Posted on 2015-03-15, 16:22

crazyc Offline

Rank Member

Rank: Member
Posts: 204
Joined: 2013-02-02, 16:17

superfury wrote:

... by reading 9 sectors to 02A0:0000 up to 02A0:2DA2.

It's reading the first FAT at the top of ram. Your int 12 is returning 0xf and 0xf * 1024 = 0x3c00. Since the FAT is 9 sectors and 9 * 512 = 0x1200 (0x2da2 is 9 * 0x512) then 0x3c00 - 0x1200 = 0x2a00. Peter's list shows the FAT read to 0x9ea00 which is 0x1200 bytes below the start of the EBDA which is at 0x9fc00.

Reply 39 of 87, by superfury

Posted on 2015-03-16, 18:25

superfury Online

Rank l33t++

Rank: l33t++
Posts: 5459
Joined: 2014-03-08, 11:25
Location: Netherlands

Fixed the INT12 handler: it now gives the correct size (it was unimplemented), 640KB to be exact. The segment is almost correct. It's at 9EE0:0000 instead of 9EA0:0000. Anyone knows the cause?

Also the final read I've logged, which is supposed to be 1 sector to 986:10, seems to go wrong?

10:01:48:54.9.0000: Function 02 called.
2
30:01:48:63.7.0000: Read 1/1 sectors from drive 00, start 0. Requested: Head: 0, Track: 0, Sector: 1. Start sector: 0, Destination: ES:BX=0070:00000281
4
50:01:49:00.6.0000: Function 02 called.
6
70:01:49:91.8.0000: Read 9/9 sectors from drive 00, start 1. Requested: Head: 0, Track: 0, Sector: 2. Start sector: 1, Destination: ES:BX=9EE0:00000000
8
90:01:52:32.9.0000: Function 02 called.
10
110:01:52:89.1.0000: Read 6/6 sectors from drive 00, start 84. Requested: Head: 0, Track: 2, Sector: 13. Start sector: 84, Destination: ES:BX=0690:00000000
12
130:01:53:01.0.0000: Function 02 called.
14
150:01:54:88.2.0000: Read 18/18 sectors from drive 00, start 90. Requested: Head: 1, Track: 2, Sector: 1. Start sector: 90, Destination: ES:BX=0690:00000C00
16
170:01:55:03.9.0000: Function 02 called.
18
190:01:56:73.6.0000: Read 18/18 sectors from drive 00, start 108. Requested: Head: 0, Track: 3, Sector: 1. Start sector: 108, Destination: ES:BX=0690:00003000
20
210:01:56:85.5.0000: Function 02 called.
22
230:01:58:50.4.0000: Read 17/17 sectors from drive 00, start 126. Requested: Head: 1, Track: 3, Sector: 1. Start sector: 126, Destination: ES:BX=0690:00005400
24

Anyone knows what's going wrong?

Filename: debugger_20150316_1916.zip
File size: 2.4 MiB
Downloads: 58 downloads
File comment: Latest debugger log with incorrect FAT destination address.
File license: Fair use/fair dealing exception

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UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io

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