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From: maa@nbires.nbi.com (Mark Armbrust)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 640kb limit on DOS?
Summary: PC problem, not DOS problem
Keywords: PS-2/50 DOS
Message-ID: <196@nbires.nbi.com>
Date: 9 Dec 88 17:43:15 GMT
References: <8043@ihlpl.ATT.COM> <3521@nicmad.UUCP>
Reply-To: maa@nbires.UUCP (Mark Armbrust)
Distribution: na
Organization: NBI Inc, Boulder CO
Lines: 26

In article <3521@nicmad.UUCP> brown@nicmad.UUCP (Vidiot (Vid-e-it)) writes:
>In article <8043@ihlpl.ATT.COM> nala@ihlpl.ATT.COM (A. Flora-Holmquist) writes:
>
>NO version of DOS allows for anything except 640K.  OS/2 programs will.
>Programs like Lotus 1-2-3 use expanded memory to do stuff.  This skirts the
>DOS memory issue.
>
I guess I better not tell this to my Tandy 2000 with 768K of memory or my NBI
2000 with 800K of DOS memory.

The problem is that PC clones have video memory starting at 0C000h which limits
contiguous low memory (The only memory normally used by DOS) to 640K.  This is
a design limitation that made sense when the PC was first introduced with only
64K of memory and 640K seemed like more than you would ever need in a PERSONAL
computer.

Note that the first "personal" computer I owned [1/3 of] was an IBM 1620 with
20K of memory and a card read/punch and console typewriter for I/O.  We later
got a line printer and two disk drives (1 meg each on a 5? platter 16" diameter
pack).  It's amazing where this industry has gone in the last 20 years; where
do you suppose it will be 20 years hence?

Happy Hacking
Mark
D
got a line printer and two disk drives (1 meg on a 4 platter