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From: gwyn%brl-vld@sri-unix.UUCP
Newsgroups: net.unix-wizards
Subject: Re:  Levels of UNIX, an opinion, a question
Message-ID: <16704@sri-arpa.UUCP>
Date: Thu, 9-Feb-84 15:58:16 EST
Article-I.D.: sri-arpa.16704
Posted: Thu Feb  9 15:58:16 1984
Date-Received: Mon, 20-Feb-84 01:07:59 EST
Lines: 9

From:      Doug Gwyn (VLD/VMB) 

The early UNIXes for memory-managed (KT11) PDP-11s were available for
the PDP-11/40 as well as the PDP-11/45.  The /40 architecture was
similar to the more familiar /34 in that it had Kernel & User modes
but not separate Instruction & Data spaces.

Two "modes" are both necessary and sufficient for controlled resource
sharing with the typical memory manager architecture.