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Mail Archives: djgpp/2001/02/07/20:19:34

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, 07 Feb 2001 23:25:44 +0000
Organization: Customer of Energis Squared
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References: <3a80a97c$0$96560$272ea4a1 AT news DOT execpc DOT com> <200102070231 DOT VAA23644 AT envy DOT delorie DOT com>
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

DJ Delorie <dj AT delorie DOT com> wrote:

> > Could this limit be removed in the next version of the C library?
> > Or raised to 21 sectors? The Win95 install floppies have
> > 21 sectors per track (1.68 meg per disk), as do various
> > demo disks, OS boot disks, etc.
> 
> It can be raised pretty easily, but making it dynamically adjust will
> be trickier.

> Does anyone know of any floppies with more than 21 sectors that the
> BIOS calls support?

Here is a reply I received from tom AT toms DOT net in relation to booting
Linux from an oversize floppy, it might have some relevance here.  

> Well, many bioses will not boot with the 'compact' option, because they
> don't know how to deal with a full-track 21-sector read.  They can read
> one sector at a time up to track 21, but if you say, 'read 21 tracks to
> the buffer starting at track 0', they choke.  So, with LILO you have to
> NOT have the 'compact' option.  Now, in the case of the kernel loading,
> directly without LILO, maybe it is combining the reads the same way and
> failing that way?
> 
> -Tom

If I understand this correctly it means that certain BIOS
implementations limit the read buffer size.  On the other hand I could
just as easily have the wrong end of the stick... ;-)

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