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From: hammond@petrus.UUCP (Rich A. Hammond)
Newsgroups: net.arch
Subject: Re: RISC and MIPS
Message-ID: <446@petrus.UUCP>
Date: Tue, 6-Aug-85 08:28:12 EDT
Article-I.D.: petrus.446
Posted: Tue Aug  6 08:28:12 1985
Date-Received: Mon, 12-Aug-85 03:01:34 EDT
References: <419@kontron.UUCP> <237@weitek.UUCP> <437@petrus.UUCP> <1432@peora.UUCP>
Organization: Bell Communications Research, Inc
Lines: 17

> >...  The Berkeley RISC's have no  absolute  addressing  mode ...
> >I'll accept RISCs when I see one runnning 4.3 BSD faster than an 11/780.
> 
>         I would like to point out that the IBM 370 (usually considered
> 	a CISC :-> ) doesn't have absolute addressing and that it only
> 	has a displacement of 2**12 bytes. They seem to be able to get
> 	some rather large operating systems, including UNIX, to run on
> 	it.

I never claimed it was impossible to get something running, I was more
concerned with whether the RISC retains its speed advantage when faced
with large amounts of absolute addressing.  Perhaps a couple global registers
used as base registers (ala IBM 360) would cover the commonly accessed
global data structures (or a smart loader would pack most of them together).
Anyway, the RISC claims will always be slightly dubious to me until I
actually see a machine performing as claimed in a real situation.
Hidden gotchas have a way of getting missed in paper exercises.