Article View: comp.arch
Article #11903Re: new instructions
From: abaum Allen Baum
Date: Fri, 31 May 1991 08:58
Date: Fri, 31 May 1991 08:58
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1559 bytes
In article <12947@mentor.cc.purdue.edu> hrubin@pop.stat.purdue.edu (Herman Rubin) writes: >This points out another reason for cheap instructions at little cost. >There are a rather large number of cases in which unsigned arithmetic >is needed. In fact, the EMUL description in the VAX manual even >indicates that, for multiple precision arithmetic, this is quite >definitely the case. > >Now how much additional silicon would it take to provide both signed >and unsigned? I couldn't let this go by. Herman, I accept the fact that you know far more about numerical problems and what you need to speed them up. (Note that this is damning with faint praise. Its easy to know more than I do) However, you are not a hardware designer. Do not presume that because unsigned & signed multiply are both multiplies, that including both is cheap. It may not be the case. Boothe style mults. are implicitly signed, for example. To pretend they aren't mean multiplying two 33 bit numbers. This is just one example. There are others from your postings.
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!noao!ncar!elroy.jpl.nasa.gov!swrinde!mips!zaphod.mps.ohio-state.edu!caen!spool.mu.edu!uunet!mcsun!ukc!acorn!armltd!abaum From: abaum (Allen Baum) Newsgroups: comp.arch Subject: Re: new instructions Message-ID: <182@armltd.uucp> Date: 31 May 91 08:58:16 GMT References: <12947@mentor.cc.purdue.edu> Sender: abaum@armltd.uucp Distribution: comp Organization: A.R.M. Ltd, Swaffham Bulbeck, Cambs, UK Lines: 23