Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!quintus!ok
From: ok@quintus.uucp (Richard A. O'Keefe)
Newsgroups: comp.arch
Subject: Re: Why is the RT slow?
Message-ID: <691@quintus.UUCP>
Date: 17 Nov 88 01:45:31 GMT
References: <5046@polya.Stanford.EDU> <cXU-XCy00V48ECDWt=@andrew.cmu.edu>
Sender: news@quintus.UUCP
Reply-To: ok@quintus.UUCP (Richard A. O'Keefe)
Organization: Quintus Computer Systems, Inc.
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In article <cXU-XCy00V48ECDWt=@andrew.cmu.edu> jk3k+@andrew.cmu.edu (Joe Keane) writes:
>I get the impression that they were paranoid about code space, giving a
>too-complicated instruction set.  To wit:

>*  Shift paired.  Where else do they pair registers?

Speaking of which, could someone explain to me what those instructions
are good for, and how best to do double-length shifts?

I doubt whether any of the points Joe Keane listed really explains why
the old RTs were roughly halfway between a Sun-2 and a Sun-3/50 on a
logarithmic scale of speed.  There are supposed to be newer versions
that are rather faster.  My guess is that it was a marketing decision:
IBM decided to scale the thing to what they thought people would buy
and guessed wrong.