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From: karl@ddsw1.MCS.COM (Karl Denninger)
Newsgroups: comp.sys.ibm.pc
Subject: Miniscribe 3085 on Dos3.3?
Message-ID: <[4368.4]comp.ibmpc;1@ddsw1.MCS.COM>
Date: 18 Jul 89 20:00:09 GMT
References: <36300051@iuvax> <[4368.3]comp.ibmpc;1@ddsw1.MCS.COM>
Lines: 40

>Response 2 of 3 (4368) by andyross at ddsw1.MCS.COM on Mon 17 Jul 89 17:55
>[Andrew Rossmann]
>
>>  Resp: 1 of 1 by karl at ddsw1.MCS.COM
>>Author: [Karl Denninger]
>>...
>>Dos 4.1 uses a larger bit table for the FAT, and thus can deal with larger
>>disks without changing the allocation size...
>
>  This is not true. DOS 4, when using partitions >32M still uses the
>same 16-bit FAT it uses under DOS 3.x. 
....
>0 and 65535 (0000 - FFFF). Since sectors are usually 512 bytes,
>65536*512 bytes = 33554432 bytes = 32M. DOS 4 (and Compaq DOS 3.31)
>supports an alternative entry method that uses 32-bit sector numbers. DOS 4
...

But Andy, that is what I said!  The FAT is _larger_ (at least for big
partitions it is).

>DOS parameter block and 32h, Get DOS Parameter Block. Apparantly, the
>number of sectors for FAT entry is now a WORD instead of a BYTE. This has

As in the FAT is (or may not be, depending on disk drive size) not the same
size as it was before.......

Run utilities that don't know the difference on a large DOS4 partition, and
watch your FAT (and probably root directory) get munched.  I've seen it
happen, and it's not pretty.

This is one of the reasons we don't encourage the use of DOS4.  While the
direct large partition support is nice, it's not guaranteed to be compatible
with all the utility software out there.  And I _hate_ having to pick up the
pieces when a customer gets hosed by some software that is supposed to
"optimize" his or her disk drive, etc...

--
Karl Denninger (karl@ddsw1.MCS.COM, <well-connected>!ddsw1!karl)
Public Access Data Line: [+1 312 566-8911], Voice: [+1 312 566-8910]
Macro Computer Solutions, Inc.  "Quality Solutions at a Fair Price"