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From: sichermn@beach.csulb.edu (Jeff Sicherman)
Subject: UMB Support (was: Re: DOS 5.0 upgrade ?)
Message-ID: <1991Jun21.171733.5636@beach.csulb.edu>
Organization: Cal State Long Beach
References: <811@wa3wbu.UUCP> <1991Jun21.082150.11675@csc.canberra.edu.au>
Date: Fri, 21 Jun 1991 17:17:33 GMT

In article <1991Jun21.082150.11675@csc.canberra.edu.au> act@softserver.canberra.edu.au (Andrew Turner) writes:

  [  deleted upgrade details ]

>
>3. Microsoft uses the following terminology to describe memory:
>
>	BASE MEMORY		:	0-640 Kb
>	(CONVENTIONAL MEMORY)
>	UPPER MEMORY AREA	:	640 Kb - 1 Mb
>	HIGH MEMORY AREA(HMA)	:	1 Mb - 1Mb+64 kB
>Due to a feature on 286's and 386's real mode execution is available in the
>HMA per the A20 address line. DOS loads Command.COM into this area if you 
>specify DOS=HIGH in CONFIG.SYS. NB COMMAND.COM has been totally rewritten and
>is RE-ENTRANT!!. This adds memory overheads of about 2.8k, I assume for each
>re-entry. You also must specify DEVICE=C:\DOS\HIMEM.SYS in config.sys.
>
>4. You will not be able to use your 384 Kb on the 286 as this requires
>EMM386.EXE to be loaded.
>
>5. To quote Microsoft:
>
>	"UMA support for 80286 class machines is not supplied in MS-DOS 5.0.
>	The choice to use EMM386.EXE as the engine for using Upper Memory
>	Blocks has been motivated by two major factors.
>
>	1. High Memory is available on both 80386 and 80286 machines. To
>	prevent having two drivers, one for each machine.
>
>	2. Development research indicated that UMB savings on 80286 class
>	machines did not offset the memory costs of the UMB driver nor
>	development time.
>
>	MS-DOS 5.0 OEMs have shown interest in developing UMA capabilities
>	into their releases. OEMs do have options that were not addressed
>	by Microsft's project, options such as Hardware and Firmware
>	solutions."
>
>Comment: Sounds like 'bull....' to me.
>
>Summary:
>	Until I try it on our 286's with 640+384 I'm not sure but it seems
>like unless you have memory in the HMA you get nothing!

   Does this mean that upper-memory (640K-1Meg) is not available for
high-loading on anything less than a 386 machine using DOS 5.0 ?

  If so, this implies that QRAM (or the like) is still necessary for
high (UMB) loading on 286-class machines ?

  Is he current QRAM compatible with DOS 5.0 ?

  In either case (DOS 5.0 works in UMB's or QRAM necessary), on an AST
Premium 286 with EEMS, is there a minimum revision level of REMM.SYS
required with either package ?

Jeff Sicherman