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From: lee@fortune.UUCP
Newsgroups: net.unix-wizards
Subject: RE: Paging != Virtual Memory
Message-ID: <1832@fortune.UUCP>
Date: Wed, 23-Nov-83 17:08:53 EST
Article-I.D.: fortune.1832
Posted: Wed Nov 23 17:08:53 1983
Date-Received: Sat, 26-Nov-83 04:47:20 EST
Organization: Fortune Systems, Redwood City, CA
Lines: 33

I do not believe that these books are supporting your idea of virtual
memory.

	'The term paging is used to describe a particular implementation
	of virtual memory and organization of main storage.'

Paging is certainly not the only virtual memory scheme.  Segmentation
is one of the others, but logical address spaces and overlaying schemes
are NOT virtual memory.

	still used by BTL UNIX as an alternate form of virtual memory
	management.

When they ( you know who ) started the UNIX development, real virtual
memory schemes were not possible for the pdp-11.  So they used the
alternate form of virtual ( bad word choice ) memory management.

	'The general techniques of automatically moving required program and data
	blocks into physical M(ain)M(emory) for execution are called virtual
	memory techniques.'

BTL UNIX allocates all required Main Memory before program executions and
ties up the memory blocks until program terminations.  This is hardly
automatic.

IBM did not invent the name of Virtual Memory for nothing ( they didn't
invent virtual memory though ).
DEC would not build the VAX ( Virtual Address eXtension ) if they can
sell the pdp-11 as virtual memory system.

	Ed Lee
	fortune!lee