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Re: [Qemu-devel] Re: Qemu floppy emulation problems - partially solved
From: |
Derek Fawcus |
Subject: |
Re: [Qemu-devel] Re: Qemu floppy emulation problems - partially solved |
Date: |
Tue, 31 Aug 2004 17:55:36 +0100 |
On Wed, Aug 18, 2004 at 05:35:19PM +0200, Mike Nordell wrote:
> Johannes Martin wrote:
>
> 1. diskette_param_table in rombios.c from Bochs is too short. It neeed two
> more bytes, else e.g. NT believes the floppy only got 31 cylinders (the code
> following the table begins with "push ds", 0x1e, and that just happens to be
> "maximum track" NT expects). Append:
> db 79
> db 0
>
> This is obvious if looking at the registry value
> HKLM\HARDWARE\DESCRIPTION\System\MultifunctionAdapter\x\DiskController\y\Flo
> ppyDiskPeripheral\0\Configuration Data.
>
> (x, y was 5 and 0 respectively on a real machine, but you might experience
> local fluctuations)
>
> Compare the last two bytes from a real system (working) with a non-working
> QEMU-installed system.
Well that would seem to be an error in the NT code, or we're triggering
something in the NT code which makes it seem to think there should be
a larger table.
The original table was only 11 bytes (as in the Bochs BIOS), you can
look at the interrupt list to see. It seems there is an enhancement
that adds an additional 3 bytes.
However from the layout of the BIOS, it looks as if there is no room
to expand the table in place, one'll have to have the param table pointer
(int 1e) point somewhere else.
Anyway, I hacked something up if you want to try...
The diff is at http://www.employees.org/~dfawcus/rombios.c-diff, and the
rom image is at http://www.employees.org/~dfawcus/bios.bin
I've not tried your other diffs yet.
DF
Format of diskette parameter table:
Offset Size Description (Table 01264)
00h BYTE first specify byte
bits 7-4: step rate (Fh=2ms,Eh=4ms,Dh=6ms,etc.)
bits 3-0: head unload time (0Fh = 240 ms)
01h BYTE second specify byte
bits 7-1: head load time (01h = 4 ms)
bit 0: non-DMA mode (always 0)
Note: The DOS boot sector sets the head load time to 15ms,
however, one should retry the operation on failure
02h BYTE delay until motor turned off (in clock ticks)
03h BYTE bytes per sector (00h = 128, 01h = 256, 02h = 512, 03h = 1024)
04h BYTE sectors per track (maximum if different for different tracks)
05h BYTE length of gap between sectors (2Ah for 5.25", 1Bh for 3.5")
06h BYTE data length (ignored if bytes-per-sector field nonzero)
07h BYTE gap length when formatting (50h for 5.25", 6Ch for 3.5")
08h BYTE format filler byte (default F6h)
09h BYTE head settle time in milliseconds
0Ah BYTE motor start time in 1/8 seconds
---IBM SurePath BIOS---
0Bh BYTE maximum track number
0Ch BYTE data transfer rate
0Dh BYTE drive type in CMOS