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From: lyang%scherzo@Sun.COM (Larry Yang)
Newsgroups: comp.arch
Subject: Re: What should be in hardware but isn't
Message-ID: <30382@sun.uucp>
Date: Thu, 8-Oct-87 13:55:33 EDT
Article-I.D.: sun.30382
Posted: Thu Oct  8 13:55:33 1987
Date-Received: Sun, 11-Oct-87 03:58:26 EDT
References: <581@l.cc.purdue.edu> <8646@utzoo.UUCP> <705@gumby.UUCP> <8668@utzoo.UUCP>
Sender: news@sun.uucp
Reply-To: lyang@sun.UUCP (Larry Yang)
Organization: Sun Microsystems, Mountain View
Lines: 38

In article <8668@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes:
>Nope, sorry, you have misunderstood slightly.  I wasn't saying "the 68881
>is more accurate than carefully-implemented double-precision software such
>as one would expect from e.g. MIPSco"; I was saying "the 68881 is more
>accurate than the sloppy first-cut software that one confidently expects
>XYZ Vaporboxes Inc. to ship as its `production' release".  The point is not
>that the 68881 has inherent advantages over software, but that it represents
>a *cheap* *prepackaged* high-quality solution.  In principle one could find
>the same thing in software, but commercial realities make this unlikely
>unless it comes from a university:  the 68881 can be cheaply and widely
>sold at a profit because *it cannot be pirated easily*.
>
>I agree that the right way to do transcendentals is in software, with help
>(e.g. extended-precision arithmetic) in the hardware when appropriate.
>But how much carefully-written software can you buy for the price of one
>68881?

How much more time would Motorola buy if they didn't do transcendentals
in micro/nanocode and had software engineers write libraries that they
could sell to customers?  Could the 881 be fit onto a smaller die (i.e.,
easier layout, better yield)?  What's wrong with Motorola saying:
"Here's this wonderful fp chip we've made.  It does all the basic
fp operations really fast.  If you want to do sin, cos, and stuff, then
here are the software library routines that are guaranteed to work."
Are there no competent software engineers at these IC houses?

I'll have to admit that I haven't designed any floating point arithmetic,
so if I'm way off base, someone please correct me. (Of course, I didn't
have to request this... :-) But it would seem that much would be gained
from the chip design/fab/test area if the sweating over complex functions
would be moved to the software realm.

*************************************************************************

--Larry Yang [lyang@sun.com,{backbone}!sun!lyang]|   A REAL _|> /\ |  _   _   _ 
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    Hobbes: "Why do we play war and not peace?"  |          <|_/ \_| \_/\| |_\_|
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