Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!helios.ee.lbl.gov!nosc!simasd!pnet07!johnlee
From: johnlee@pnet07.cts.com (John Wiley)
Newsgroups: comp.sys.ibm.pc
Subject: Re: FAT problems
Message-ID: <22@simasd.UUCP>
Date: 21 Oct 89 05:25:22 GMT
Sender: news@simasd.UUCP
Organization: People-Net [pnet07], San Diego, CA
Lines: 17

Jonathan Lavigne writes:

>If the first two bytes of the FAT on your hard disk aren't "F8FF"

The first byte of each copy of the FAT is called the "Media Descriptor Byte,"
and you're right - it should be F8 according to "THE MS-DOS ENCYCLOPEDIA" by
Duncan.  He also points out that this same value should be found in the "Boot
Record," which is logical sector 0 of the partition (on most C: drives, that's
BIOS sector 1, Track 0, Side 1).  Offset 15 hex (21 decimal) is the location
of the Media Descriptor in the Boot Record (counting from offset 0).  If you
do try fixing the Media Descriptor Byte in the FATs, it would be good to check
the one in the Boot Record too.  Assuming you can get it to work, it would be
a good idea to back it up and do a low-level format.  That's the best
insurance for future data integrity.   -good luck.
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