Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cwjcc!hal!ncoast!allbery
From: allbery@ncoast.ORG (Brandon S. Allbery)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Problem of breaking DOS 640K RAM limit?
Message-ID: <13477@ncoast.ORG>
Date: 15 Mar 89 02:28:27 GMT
References: <74032HJW2@PSUVM> <15373@cup.portal.com> <1345@ccncsu.ColoState.EDU> <1429@cfa.cfa.harvard.EDU>
Reply-To: allbery@ncoast.UUCP (Brandon S. Allbery)
Followup-To: comp.sys.ibm.pc
Organization: Cleveland Public Access UN*X, Cleveland, Oh
Lines: 27

As quoted from <1429@cfa.cfa.harvard.EDU> by ward@cfa.harvard.EDU (Steve Ward):
+---------------
| I believe there are a few PC bus memory boards on the market which
| are half-size and allow adding up to 384K of memory.  Such a board
| could possibly be used to add memory above, but contiguous with the
| 640K.  Now all you to do is disassemble your BIOS chip and modify it!
+---------------

Don't try this at home, kids.

Steve has apparently forgotten about video memory, which starts at the
following addresses:

		MDA and Hercules...	B0000H
		CGA...			B8000H
		EGA and VGA...		A0000H

Thus, if you use EGA or VGA, 640K is the absolute limit to main memory:
anything above it is EGA/VGA RAM.  If you use a Herc clone, you can go to
720K.  If you're so backwards as to still be using a CGA, you can go to 752K.

++Brandon
-- 
Brandon S. Allbery, moderator of comp.sources.misc	     allbery@ncoast.org
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