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From: philip@amdcad.AMD.COM (Philip Freidin)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Problem with telling UNIQ 286B its own memory sizes
Message-ID: <17520@amdcad.AMD.COM>
Date: Tue, 14-Jul-87 16:47:16 EDT
Article-I.D.: amdcad.17520
Posted: Tue Jul 14 16:47:16 1987
Date-Received: Thu, 16-Jul-87 06:59:46 EDT
References: <19665@ucbvax.BERKELEY.EDU>
Reply-To: philip@amdcad.UUCP (Philip Freidin)
Distribution: world
Organization: Advanced Micro Devices, Inc., Sunnyvale, Ca.
Lines: 30

< owner of UNIQ 286B reprots problems with splitting 1 meg of ram >

Because of the way memory decode is done, AT-clone motherboards differ in the
way they handle more than 640k on the mother board.

Some allow for the 1 meg to be split at the 640k boundary, and the remaining
384 k is remapped to the 1 meg boundary. The logic for this requires a few
chips, and the better motherboards do this.

Others, allow for 1 meg of ram, and either give you 640k and ignore the rest,
or split at the 512 k boundary, and remap the second 512 to the 1 meg boundary
The logic for this is much simpler, and is therefore much more common in the
at-clone cards.

If your card is the second category (and your description indicates that it
certainly is), there is nothing you can do with bios proms or setup sw
that will fix the problems. 

I recomend you run 640k of main memory, ignore the missing 384k, and
buy some 2 or 4 meg ram cards for the ram disk

Hope this is of some marginal help


Philip Freidin @ AMD SUNYVALE on {favorite path!amdcad!philip)
Section Manager of Product Planning for Microprogrammable Processors
(you know.... all that 2900 stuff...)
"We Plan Products; not lunches" (a quote from a group that has been standing
				 around for an hour trying to decide where
				 to go for lunch)