From:	Jason Green <news AT jgreen4 DOT fsnet DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp,alt.os.development
Subject:	Re: Help wanted (was Re: 18-sector limit with biosdisk())
Date:	Sat, 24 Feb 2001 23:39:46 +0000
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Firstly, the problem I had originally with booting Linux kernel from
an over-sized floppy is (just) now solved.  It seems that increasing
sectors and/or tracks does not cause a problem, but multiple sector
size (mss) does not make the kernel happy when booting.  Sorry if I
led you to chase this unecessarily - although I would still believe
what Tom said about some BIOSes being buggy.

NoEmailAds AT execpc DOT com (Chris Giese) wrote:

> >> Otherwise, I could write a small test program to check if the BIOS
> >> really does limit reads to 18 sectors.
> >
> >That might also be a good idea.
> 
> OK, here it is:
> 	http://www.execpc.com/~geezer/temp/ftest.c
> 	http://www.execpc.com/~geezer/temp/ftest.exe
> 
> Please download it and try it. If it reports that your BIOS
> limits INT 13h reads to 18 sectors, let me know.

No problem here, but I no longer suspect this BIOS as buggy.

This is the output from ftest:

This program tests if BIOS function INT 13h AH=02
limits multi-sector reads to 18 sectors.
You need an "oversized" FAT12- (DOS-)formatted
floppy, with 19-21 sectors per track

Reading sector 0 of floppy disk...
Checking for FAT filesystem...
Boot sector says 21 sectors per track
Patching floppy parameter table (FPT)...
	Current FPT at address 0:522
	Current maximum sectors-per-track value in the FPT is 18
	New FPT at address 1211:0
	New maximum sectors-per-track value in the FPT is 96
Reading 21 sectors from track 0, head 0...
Restoring old FPT...

Success. The INT 13h function in your BIOS does
not appear to restrict reads to 18 sectors

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