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Article #44027

Re: How do VGA cards use the C000 memor

#44027
From: CUMMINGS
Date: Sun, 11 Mar 1990 21:10
32 lines
2001 bytes
/* Written  9:26 am  Mar 11, 1990 by lane@cs.dal.ca in S55:comp.sys.ibm.pc */
/* ---------- "How do VGA cards use the C000 memor" ---------- */

According to 386MAX, I have a ROM BIOS extension at C000-C400 which
seems resonable (I beleive this is typical for a VGA).  However,
386MAX seems confused as to whether there is ROM or RAM at C400-C800.
Whatever, it won't use that area for high DOS memory.  DEBUG says
there's something at C400-C600 but nothing (FF's) at C600-C800.

/* End of text from S55:comp.sys.ibm.pc */

What kind of ROM (PROM, EPROM, EEPROM, etc) is on your VGA card?
If you are right, and your VGA BIOS is from C000-C5FF, then it's
24K large.  If your VGA card has a 32Kx8 EPROM on it, they may have only
programmed the first 24K (don't 27xxx EPROMs contain all FFs when erased?)
Probably cheaper to manufacture a card with one slightly larger EPROM than
with 3 smaller ones....


============================================================================
Kevin J. Cummings                       Prime Computer Inc.
20 Briarwood Road                       500 Old Connecticut Path
Framingham, Mass.                       Framingham, Mass.

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!mintaka!bloom-beacon!primerd!ENI!S55!CUMMINGS
References: <5657@<1990Mar8>

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From: CUMMINGS@S55.Prime.COM
Newsgroups: comp.sys.ibm.pc
Subject: Re: How do VGA cards use the C000 memor
Message-ID: <132000041@S55.Prime.COM>
Date: 11 Mar 90 21:10:00 GMT
References: <5657@<1990Mar8>
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Nf-ID: #R:<1990Mar8:-565700:S55:132000041:000:1525
Nf-From: S55.Prime.COM!CUMMINGS    Mar 11 21:10:00 1990