Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!killer!chasm
From: chasm@killer.DALLAS.TX.US (Charles Marslett)
Newsgroups: comp.unix.i386,comp.sys.ibm.pc
Subject: Re: What would you use for Fast Floating-Point?
Summary: MUCH MUCH FASTER!
Keywords: Floating-point,Coprocessors
Message-ID: <8437@killer.DALLAS.TX.US>
Date: 23 Jun 89 03:50:27 GMT
References: <2105@randvax.UUCP>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 41

In article <2105@randvax.UUCP>, edhall@randvax.UUCP (Ed Hall) writes:
> I want to put together a reasonably priced 386-based system which will
> support blindingly fast floating-point calculations.  To give you an
> idea of how fast I want, I currently have a 286-based system with a
> 10Mhz '287 in it--and I need something at least 10 times faster.
> This means something with performance close to 1 MFlop.
> 
> Does anyone know just how much faster the '387 is compared to its
> lowly cousin the '287?  How about a coprocessor like the Weitek?

The Intel '387 processor is about 3 or 4 times faster than the '287 at
the same clock speed.  I think the Weitek chip is perhaps 2 or 3 times that
speed if the code is well written (it can, if the code is just copied over,
be slower, however).

With Microsoft C (5.1), I get about 160,000 Flops on a 20MHz Everex Step/386
with a 387.  And on a 10 MHz AST Premium/286 with a 287, I get about 28,000
(AST runs the 287 at 8 MHz).

For those watching IIT (and their 287/387 clones), the IIT 287 is a lot faster
than the Intel part (say 2x or 3x), but the IIT 387 is much closer to Intel's
speed.  The IIT '387 will run about 200,000 Flops in the example above (25-35%
faster, that is).  I really reccommend it for anyone needing just a little
push doing fp stuff on a 286!

As soon as I get a real production IIT part, I'll post some real measurements.

Charles Marslett
chasm@killer.dallas.tx.us
> And, before you get any ideas about some add-in vector processor,
> whatever I get will have to be supported by some reasonable version
> of UNIX, and be accessable from C.
> 
> If there is any interest, I'll summarize any advice I get and post.
> 
> Thanks!
> 
> 		-Ed Hall
> 		edhall@rand.org
> 		..!uunet!edhall@rand.org
> 		..!decvax!randvax!edhall