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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: <26287@sequent.UUCP>
Date: 13 Dec 89 16:38:16 GMT
References: <882@crash.cts.com> <29915@genrad.UUCP>
Reply-To: norsk@crg2.UUCP (Doug Thompson)
Organization: Sequent Computer Systems, Inc.
Lines: 37

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
>

While working at Tandon Computer Corp at the time Compaq had released 3.31 and 
prior to MS/IBM releasing 4.0x I had to grapple with the support of large
partitions in our Tandon MS-DOS. Compaq couldn't wait (good for them!) for
MS/IBM to release a DOS that handled large partitions and upgraded their
OEM kit of 3.30 to handle large partitions (The major problem was the
abilitly of the code and data structures in the kernel and the drivers to
address more than 2^^16 sectors of disk) by increasing disk sector addresses.
They "stole" a few unused/reserved fields from internal DOS data 
structures and added the address and other new fields to support this.

The problem we found out was that MS/IBM did, in principle, the same thing
by added the required new fields. In implementation, there are some
mutual exclusive data structure members between Compaq 3.31 and PC-DOS 
4.0x. One has to be careful when mixing drivers and "system" programs
between the two.

BTW: MS asked Compaq not to do the 3.31 release, but to wait "awhile"
longer. And they asked Tandon Not to implement the Compaq scheme, but
rather wait for 4.0x. This was back in Jan '88. 


-- 
Douglas Thompson		UUCP: ..{tektronix,ogicse,uunet}!sequent!norsk
Sequent Computer Systems	Phone: (503) 526-5727
15450 SW Koll Parkway	!"The scientist builds to learn;the engineer learns in
Beaverton OR 97006	!order to build."  Fred Brooks