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From: norsk@sequent.UUCP (Doug Thompson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: DOS 3.3 versus 4.0
Message-ID: <26289@sequent.UUCP>
Date: 13 Dec 89 16:46:45 GMT
References: <882@crash.cts.com> <29915@genrad.UUCP> <4491@ur-cc.UUCP>
Reply-To: norsk@crg2.UUCP (Doug Thompson)
Organization: Sequent Computer Systems, Inc.
Lines: 39

In article <4491@ur-cc.UUCP> ctne_ltd@uhura.cc.rochester.edu (Chris Newbold) writes:
>In article <29915@genrad.UUCP> jpn@genrad.UUCP (John P. Nelson) writes:
>>>>"Standard" DOS 3.3 does not.  But I believe that NEC has enhanced 3.3
>>>>to accommodate disks of greater than 32 MB.
>>>
>>>And so does Compaq.  Compaq MS-DOS 3.31 I am told will support DOS partitions
>>>greater than 32 Mb.
>>
>>As will any copy of MSDOS 3.31.  Microsoft added the large partition support
>>betweeen 3.30 and 3.31
>
>Does this mean that I can drop back from 4.0 to 3.31 without having to reformat
>my 60mb drive?  Compaq 3.31 is the only DOS prior to 4.0 that I've heard
>supports partitions over 32mb.  If MS 3.31 *does* do large drives, will it 
>run on a PS/2?
>
>

See my other posting on the history of 3.31. Other OEM's MS-DOS sometimes
support partitions greater than 32mb, if they roll their own DOS. I used to
work for Tandon Computer Systems, and their DOS allowed for partitons greater
than 32mb by enlarging the cluster allocation unit.

For example, partitions <= 32mb would use allocations of 4k bytes. To go
to 64mb allocation would be 8k bytes, 128mb 16kb, 256mb 32kb. The result is
on a DOS file system will small files there is alot of internal fragmentation.
Each DOS file system has a table in its boot section that provides all the
necessary info on how to access the disk. Then all that is needed is a 
correctly written table driven disk driver. It was neat. 

Yet DOS 4.0x is a better plan. They fixed the design flaw of DOS and gave
it true (at least 24-bit) long word disk addressing.


-- 
Douglas Thompson		UUCP: ..{tektronix,ogicse,uunet}!sequent!norsk
Sequent Computer Systems	Phone: (503) 526-5727
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