From: Jason Green <news AT jgreen4 DOT fsnet DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: 18-sector limit with biosdisk()
Date: Wed, 14 Feb 2001 23:47:54 +0000
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

NoEmailAds AT execpc DOT com (Chris Giese) wrote:

> What if someone wants to use 21-sector disks?
> 1. We presume they are smart enough to patch the sectors-per-
>    track value in the floppy parameter table (FPT), so the FPT
>    does not restrict them.
> 2. We fixed biosdisk(), so it does not restrict them.
> 3. Maybe the BIOS limits them to 18 sectors? I'm not sure it
>    does. I presume INT 13h will return some kind of error
>    code in this case. The BIOS is not something we can fix.

Agreed.

> >> If there is some doubt then it would be worth to do a simple test
> >> before any serious development work on libc.
> 
> Are there any popular DJGPP programs that make heavy use of
> biosdisk()?
> 
> Otherwise, I could write a small test program to check if the BIOS
> really does limit reads to 18 sectors. However, the persons doing
> the testing must have a floppy with 21 sectors per track to work
> with, e.g. the Win95 install floppies, or an oversized Linux boot/
> root disk.

I suggest to paste biosdisk() into a test program and simply 'up' the
sector limit to whatever you require, make the program self contained
and printf all the diagnostics you need.

The test might require an old motherboard - if so I will have time for
this for the next day or two.