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From: mjl@tropix.UUCP (Mike Lutz)
Newsgroups: comp.arch
Subject: Re: D-machine helped spawn RISC
Message-ID: <290@tropix.UUCP>
Date: Tue, 8-Sep-87 16:30:34 EDT
Article-I.D.: tropix.290
Posted: Tue Sep  8 16:30:34 1987
Date-Received: Wed, 9-Sep-87 06:45:58 EDT
References: <4782@sdcrdcf.UUCP>
Reply-To: mjl@tropix.UUCP (Mike Lutz)
Organization: GCA/Tropel Div. Rochester, NY 14450
Lines: 24

In article <4782@sdcrdcf.UUCP> eggert@SM.Unisys.com (Paul Eggert) writes:
>In article <288@tropix.UUCP> mjl@tropix.UUCP (Mike Lutz) writes
>
>	... the B1700 was a pleasure to work with at the microcode level (and
>	anyone who has done serious microprogramming knows what an amazing
>	statement that is!)
>What irony!  David Patterson, Mr. RISC, wrote his PhD thesis at UCLA in 1975 on
>formal verification of microcode for the D-machine (as Lutz says, really the
>Burroughs 1700).

Just to clear up a misconception: the B1700 was *not* the D-machine.  The
two were designed and built by two different divisions in Burroughs, and,
as far as I can tell, had little influence on one another.  The D-machine
had two levels of emulation; the B1700 was a vertical microengine.  I pity
the poor soul who might have tried to nanocode a D-machine to make it into
a B1700.

However, the comments on David Patterson were right on target.  What he
demonstrated in his thesis was startling to the microprogrammming community.
Most folks were just starting to address the problems of high level languages
on horizontal machines, when Patterson showed a system that a) balanced
the vertical and horizontal resource utilization in the D-machine, b) was
verifiable, and c) in one case generated a smaller & faster emulator than
one coded by hand (the accepted norm at the time)!