Path: utzoo!mnetor!uunet!rosevax!nis!meccts!mn-at1!alan
From: alan@mn-at1.UUCP (Alan Klietz)
Newsgroups: comp.arch
Subject: What's a Vax 11/780 MIP really?
Message-ID: <413@mn-at1.UUCP>
Date: 12 Mar 88 11:37:03 GMT
Organization: Roseville, MN
Lines: 47

We all know what a VAX "MIPS" is, right?  But have you ever
bothered to actually measure it?  DEC did.  A recent column in one of
the Unix trade mags reveals that the Vax 780 = 1 MIPS rule-of-thumb
may be grossly overstated.  Here are some excerpts from the April 1988
issue of Unix/World's "Inside Edge" column, by Omri Serlin,

		Recently confirmed data published by DEC staffers
	proves that the VAX 11/780, accepted by the industry and
	the press as a 1 MIPS machine, was actually less than half
	as powerful.  The discovery affecets numerous industry
	comparisons relative to the 780.

		Over the past several years, both DEC and the 
	industry as a whole seem to have accepted the notion
	that the VAX 11/780 was, more or less, a 1 MIPS machine.
	DEC publicly confirmed the fact in December 1985, when
	it published  full-page ads characterizing the VAX 8650
	as a '6 MIPS' machine; DEC officially regards the machine
	as having six times the power of an 11/780.  The number
	of performance claims by other players in the computer
	field that assume a 1 MIPS rating for the 11/780 is too
	numerous to count.

		In October 1987, one of the authors [of the DEC
	study] presented a paper on the performance of the VAX
	8800, a dual-processor machine in which each processor
	is six times as fast as the 11/780, by DEC's official
	reckoning.  This paper reported on some preliminary
	measurements that showed the 8800 processor to have
	a cycle per average instruction (CPAI) rate of 8.4. 
	At cycle time of 45ns, this translates into a MIPS rating
	of 2.65.


[End of quote.]

Therefore one VAX 780 "MIPS" is approximately 0.44 "honest-to-god"
VAX MIPS?  (HTGV MIPS?)   Or a 126% overestimate?

--
Alan Klietz
Minnesota Supercomputer Center (*)
1200 Washington Avenue South
Minneapolis, MN  55415    UUCP:  alan@mn-at1.k.mn.org
Ph: +1 612 626 1836       ARPA:  alan@uc.msc.umn.edu  (was umn-rei-uc.arpa)

(*) An affiliate of the University of Minnesota