Path: utzoo!bnr-vpa!bnr-fos!bigsur!bnr-rsc!bcarh61!schow
From: schow@bcarh61.bnr.ca (Stanley T.H. Chow)
Newsgroups: comp.sys.ibm.pc
Subject: Re: NEAT chips fiddling (was Re: Why is DOS limited to 640K? / extra RAM
Message-ID: <1368@bnr-rsc.UUCP>
Date: 14 Nov 89 23:30:46 GMT
References: <700@wrgate.WR.TEK.COM>
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Reply-To: bcarh61!schow@bnr-rsc.UUCP (Stanley T.H. Chow)
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In article <700@wrgate.WR.TEK.COM> michaelk@copper.WR.TEK.COM (Michael D. Kersenbrock) writes:
>
>>Yes, it is possible to fiddle the NEAT chip set to make it hand the
>>memory back. DOS would still have to be told to use it. If you can't find
>>the program (or if no one has written it), I can whip it up real quick.
>>This is useful only if you have on a 286 or a 386 *not* running QEMM.
>
>There's a program "EEMRAM" available archived as "eemram21.arc" that 
>will use LIM 4.0 expanded memory to add memory past 640K.  It's not
>a TSR, it just fills in memory past 640K, tells DOS about it, and exits.
>
>My XT-clone has 704K (720,896 bytes), and works just fine.  Seems that
>if the NEAT chip set were set up for expanded memory (and QEMM supplying
>the LIM driver ???), that this program might work on other machines as
>well (w/o EGA/VGA).
>
>--
>Mike Kersenbrock
>Tektronix Microprocessor Development Products
>michaelk@copper.WR.TEK.COM
>Aloha, Oregon

The problem is not quite what you think it is.

On systems with NEAT & AMI bios (like my 386), the memory is *missing*.
There are 2 Meg worth of memory chips in my machine, the POST memory
test confirms there is 2048K. By the time DOS gets control, there is
only 640K of conventional memory and 1024K of extended memory. The
region between 640K and 1 Meg is gone.

Some of the missing 384K is used for ROM shadowing. The rest is just
plain "turned-off". It is not hiding in extended memory. The CPU really
cannot talk to that memory. This is a quirk of how AMI handles NEAT.
As a consequence, QEMM cannot use that memory.

What I said in the original article is that it is possible to set the
NEAT registers so that the missing memory shows up again. You can then
use it anyway you see fit. (I also complained that QEMM does the wrong
thing with it, so that it is *better* to leave it missing).

Also, the NEAT chip set knows nothing about expanded memory. QEMM (or
some other 386 memory manager) is using the 386 MMU to implement EMS.

BTW, all these things are true for *my* 386 system. I only expect
other 386 and 286 systems to be like that.

--
Stanley Chow        BitNet:  schow@BNR.CA
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(613) 763-2831		     ..!utgpu!bnr-vpa!bnr-rsc!schow%bcarh61
Me? Represent other people? Don't make them laugh so hard.