Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!zaphod.mps.ohio-state.edu!usc!snorkelwacker!spdcc!esegue!johnl
From: johnl@esegue.segue.boston.ma.us (John R. Levine)
Newsgroups: comp.arch
Subject: Re: Integer Multiply/Divide on Sparc
Message-ID: <1989Dec29.060249.14061@esegue.segue.boston.ma.us>
Date: 29 Dec 89 06:02:49 GMT
References: <84768@linus.UUCP> <8840004@hpfcso.HP.COM> <84983@linus.UUCP> <245@dg.dg.com>
Reply-To: johnl@esegue.segue.boston.ma.us (John R. Levine)
Organization: Segue Software, Cambridge MA
Lines: 25

In article <245@dg.dg.com> uunet!dg!rec (Robert Cousins) writes:
>Actually, this debate is now closing in on 45 years old.  If you will simply
>go pull a copy of the original ENIAC papers by Von Neuman and Co. you will
>find a long and drawn out discussion of the pros and cons of adding a number
>of instructions to the basic architecture: multiplication ...

>Given the constraints of the time, both multiply and divide were considered
>quite justifiable.  However, it is interesting to note that Von Neuman didn't
>believe in floating point.  He only believed in signed fixed point.

Well, yes and no.  When von Neumann went back to Princeton to build his
own computer, the IAS machine, he used some surprisingly modern sounding
arguments ("make a small set of operations as fast as possible") to decide not
to include a hardware multiplier.  I'll dig up the citation, it's quite
interesting.

Remember that the ENIAC was nearly impossible to program, and if they had
to implement software multiplication, they'd have never gotten anything done
at all.  It was quite common to spend three days setting up a program that
would take a few seconds to run.  The IAS machine had a modern stored program
architecture so a multiplication subroutine was no big deal.
-- 
John R. Levine, Segue Software, POB 349, Cambridge MA 02238, +1 617 864 9650
johnl@esegue.segue.boston.ma.us, {ima|lotus|spdcc}!esegue!johnl
"Now, we are all jelly doughnuts."