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From: hrubin@pop.stat.purdue.edu (Herman Rubin)
Newsgroups: comp.arch
Subject: Re: standard extensions
Message-ID: <6968@mentor.cc.purdue.edu>
Date: 27 Feb 91 15:07:47 GMT
References: <1991Feb25.135057.23667@linus.mitre.org> <1991Feb27.021435.11296@bingvaxu.cc.binghamton.edu>
Sender: news@mentor.cc.purdue.edu
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In article <1991Feb27.021435.11296@bingvaxu.cc.binghamton.edu>, kym@bingvaxu.cc.binghamton.edu (R. Kym Horsell) writes:
> In article <2124@cluster.cs.su.oz.au> rex@cluster.cs.su.oz (Rex Di Bona) writes:
> >Single Cycle? For a divide instruction? On what machine? If we take a real
> >example here instead (say the 68020, or the R3000 (as I have the info just
> >behind me here, ugh, there.... lets see, the 68020... , divide, here we are:
> 
> Oh, I don't know. I kinda had the impression that there were some
> high performance divide pipelines that did give a result every cycle.
> Milage may vary however. (Perhaps giving example 68000 code was a bit
> misleading).

Of the machines I know, this is not the case.  The CYBER 205, which 
pipelines just about everything, does not pipeline divide, square root
(the same unit), or convert between decimal and binary, which I believe
also uses that unit.  The CRAY does not provide a division at all, presumably
because it could not be pipelined.  It does have a pipelined approximation to
reciprocal, and a pipelined correction factor.

This is very definitely an architecture problem, and not a language problem.
--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: (317)494-6054
hrubin@l.cc.purdue.edu (Internet, bitnet)   {purdue,pur-ee}!l.cc!hrubin(UUCP)