Path: utzoo!attcan!uunet!lll-winken!lll-ncis!helios.ee.lbl.gov!pasteur!ucbvax!tolerant.UUCP!uucp
From: uucp@tolerant.UUCP (UNIX-UNIX Cp)
Newsgroups: comp.unix.microport
Subject: Submission for comp-unix-microport
Message-ID: <8901061339.AA24929@handel.TOLERANT>
Date: 6 Jan 89 13:39:04 GMT
Sender: uuclerk@ucbvax.BERKELEY.EDU
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Path: tolerant!voder!apple!rutgers!cs.utexas.edu!natinst!bigtex!james
From: james@bigtex.cactus.org (James Van Artsdalen)
Newsgroups: comp.unix.microport
Subject: Re: missing 384K on V/386
Message-ID: <12352@bigtex.cactus.org>
Date: 3 Jan 89 03:13:09 GMT
References: <1263@altger.UUCP>
Reply-To: james@bigtex.cactus.org (James Van Artsdalen)
Organization: Institute of Applied Cosmology, Austin TX
Lines: 23

In <1263@altger.UUCP>, dirk@altger.UUCP (dirk) wrote:
> 			Where did the 384K go ?

> If you install 2MB on a Compaq 386 you'll get 640K conventional memory
> and 1024K extended memory == 1664K. When booting 386/ix it reports
> 1703936 Bytes of real memory. So, where are they ?

Not all motherboard hardware supports mapping the "missing" 384K into
the extended memory space.  Some can map that 384K to the 1meg mark,
but only if there is no other memory at the 1meg address.  It's just a
fact of life: too many chipset designers have a Mess-DOS mindset.  I
should point out that shadow RAM *is* a tremendous win under DOS...

> [...] On a Chips+Tech chipset I saw an option to enable shadow
> memory by 16K page increments.

386/ix is probably only using the 0-640K and > 1meg memory.  A clever
trick would be to enable all of the shadow memory possible in
read/write mode and use it too, meaning you'd lose only the memory
used by the video display and any memory mapped devices.
-- 
James R. Van Artsdalen          james@bigtex.cactus.org   "Live Free or Die"
DCC Corporation     9505 Arboretum Blvd Austin TX 78759         512-338-8789