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From: brown@nicmad.UUCP
Newsgroups: net.micro.pc
Subject: DOS3.20 and DOS3.10 Incompatibilities
Message-ID: <668@nicmad.UUCP>
Date: Mon, 28-Apr-86 18:09:32 EDT
Article-I.D.: nicmad.668
Posted: Mon Apr 28 18:09:32 1986
Date-Received: Fri, 2-May-86 22:38:58 EDT
Distribution: net
Organization: Nicolet Instrument Corp. Madison WI
Lines: 47

[How I love these mods that make things incompatible!!!!]

Here is one for you PC experts out there.  I dig into a few things of this
machine, this this has stumped me. :-(

I was running two 10MB hard disks, with the mod to make them 2K clusters.
When I started up PC-DOS 3.20 from diskette, I couldn't read the hard
disks.  It was as if the hard disk was being seen as 4K clusters, etc.
Well, to make a long story short, I backed up and reformated the hard disks.
The format let the drives be 2K in cluster size.  But now 3.20 understands
the drives, and if I start up 3.10 from diskette, it can't read the drives.

I then downloaded the INFO.EXE program from 'PC Tech Journal', which lets
me display the parameters of the hard drive.  Since the program was written
for 2.00 through 3.10 DOS, I had to change the one byte in the code to let
it see PC-DOS 3.20 (I don't have the Microsoft C Compiler).  When I run
INFO on the hard drive, with 3.20, everything is as expected.  But, when I
run INFO on the hard drive, with 3.10, I get:
	FAT entries are 12 bits, instead of 16;
	Cluster size is 4096, instead of 2048;
	Hidden from DOS: 3 sectors, instead of 1;
	FAT: 16 sectors, instead of 21

The following is the partition table:
	Partition 1 through 3 is zero
	Partition 4: 80 00 02 00 04 03 51 30 01 00 00 00 03 51 00 00

The following is the DOS partition's boot record:
	EB 34 90 49 42 4D 20 20 33 2E 32 00 02 04 01 00 02 00 02 03 51
	F8 15 00 11 00 04 00 01 00

I don't have the partition or boot record from DOS 3.10.  I destroyed them
before I really knew what I was doing.

So, what I am asking is does anyone understand why different versions of PC-DOS
does not understand the other version's format of the hard disk (modified)?
Does it have anything to do with booting up on floppy?  Any ideas would be a
help is understanding what this thing is doing.

Thanks in advance.
-- 

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