Path: utzoo!utgpu!watserv1!payne
From: payne@watserv1.waterloo.edu (Doug Payne [DCS])
Newsgroups: comp.sys.next
Subject: /dev/mem and real memory size
Message-ID: <1315@watserv1.waterloo.edu>
Date: 2 Mar 90 23:37:40 GMT
Reply-To: payne@watserv1.waterloo.edu (Doug Payne [DCS])
Distribution: world
Organization: U. of Waterloo, Ontario
Lines: 14

I've written a small program which reads consecutive 1Kb blocks from
/dev/mem until it gets an error.  It was done in an attempt to figure
out the real memory size of a (non-NeXT) system which doesn't display
the size at boot time, and which is exhibiting behaviour which
indicates that it is using less real memory than it physically has.
Anyway, I decided to try it on the NeXT out of curiousity.  I can read
16Mb worth (16,384 1Kb blocks) on an 8Mb system!  Any ideas why this
occurs?  I've tried it on various other machines ranging from a Sun
SPARCServer390 to an IBM PS/2 running AIX, all with the expected
results.  Howcome the NeXT differs?  (It really does have 8Mb of
memory; I checked the board, and it claims 7.99Mb at boot time ...
close enough).

../doug