Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!killer!csccat!jack
From: jack@csccat.UUCP (Jack Hudler)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 12-bit or 16-bit FAT entry
Message-ID: <1350@csccat.UUCP>
Date: 5 Jul 88 20:15:43 GMT
References: <5930009@hpcupt1.HP.COM>
Reply-To: jack@csccat.UUCP (Jack Hudler)
Organization: Computer Support Corporation. Dallas,Texas
Lines: 29

In article <5930009@hpcupt1.HP.COM> andrews@hpcupt1.HP.COM (Edward E. Andrews) writes:
>How can I determine whether the FAT is using 12-bits or 16-bits per entry?
>Is there a DOS call that specifically states: 12(16)-bit FAT, or does it
>need to be infered (e.g. via DOS version [>3.2] or disk size [>32M])?

You need the book MEMORY RESIDENT UTILITUES,INTERRUPTS, AND DISK
MANAGMENT With MS&PC DOS. By Micheal Hyman, ISBN 0-943518-73-3,
Published by Management Informations Sources, Inc
	     1107 N.W 14th Ave.
	     Portland,Oregon 97209
	     +1 503 222 2399

This book goes into the disk rather well.
A disk that uses a 12bit fat is usually a hard disk containing less than
31111 sectors per disk bytes 19 and 20 in the boot record. I personally
dislike reading the boot record because there are a few disk managment
drivers out there for partitioning hard drives that neglect in makeing
a boot record on the non-bootable partition. I use the undocumented
DOS call ah=32h dl=drive {0=def;1=a;2=b..} int21 ds:bx point to
the drivers disk parameter block. Using this a disk system that uses 
12 bit fats has less than 4087 for it's highest cluster - 1.

Either way both have it's pit falls ;-).

					Jack Hudler


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