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From: hrubin@pop.stat.purdue.edu (Herman Rubin)
Newsgroups: comp.arch
Subject: Re: float/float = integer, remainder
Message-ID: <12315@mentor.cc.purdue.edu>
Date: 14 May 91 21:00:28 GMT
Article-I.D.: mentor.12315
References: <9105130317.AA09926@ucbvax.Berkeley.EDU> <12248@mentor.cc.purdue.edu> <1991May14.141623.16040@murdoch.acc.Virginia.EDU>
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In article <1991May14.141623.16040@murdoch.acc.Virginia.EDU>, clc5q@hemlock.cs.Virginia.EDU (Clark L. Coleman) writes:
> In article <12248@mentor.cc.purdue.edu> hrubin@pop.stat.purdue.edu (Herman Rubin) writes:
> >In article <9105130317.AA09926@ucbvax.Berkeley.EDU>, jbs@WATSON.IBM.COM writes:

			..................

> The Cody/Waite algorithm does do float -> integer conversion at one point,
> and the presence of Herman's requested instruction would make it
> possible to do things differently. But, should we be requesting a
> floating multiply instruction that produces an integer result and
> a floating fractional result? This might be faster. Or are there other
> routines that cannot be altered from a divide to a multiply and are
> important enough to justify the requested divide instruction ?

There are quite a few machines which cannot even find the integer part
of a floating number in hardware.  This can be a substantial problem.

There are situations in which the floating fractional result of the
multiplication leads to problems.  The way division is now going on
most computers, it might be just as good to do a multiply and subtract.
So at least float -> integer part, in both integer and floating, is
needed.
-- 
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)