Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!sun!kilowatt!raz
From: raz@kilowatt.uucp (Raz- Berry)
Newsgroups: comp.sys.amiga.tech
Subject: Re: 80860 as a math processor
Summary: Thats a kluge.
Keywords: Super bit belching
Message-ID: <33756@kilowatt.uucp>
Date: 28 Apr 89 05:06:59 GMT
References: <15147@gryphon.COM>
Reply-To: raz@sun.UUCP (Steve -Raz- Berry)
Organization: Sun Microsystems, Mountain View
Lines: 77

In article <15147@gryphon.COM> richard@gryphon.COM (Richard Sexton) writes:
)In article <33739@kilowatt.uucp> raz@sun.UUCP (Steve -Raz- Berry) writes:

))I think we are a little confused here, There is no way that the Weitek
))can possibly emulate a 68881. Not without a major hardware kluge. I think 
))that richard means that the Weitek chip SET (IU and FPU) together function
))simalirly to the 680X0 and coprocessor series.

)No, Richard meant it was a co-processor, like the 68881/2. Thats what
)the ads implied.

Your kidding. I don't claim to know all, but I thought I woulda 
heard that. Oh well.

)So I called Weitek.

)Buggers.

)The stupid thing is memory mapped. You write the operands into
)memory addresses, then give it an operation, then poll it for
)completion. Some co-processor.

Not a true co-processor if you ask me, ok so it fits the description...
but it's a kluge.

)Some performence data: 

)Linpack - single precision 8 MFLOPS
)	  double           6 MFLOPS
)Whenstone Single precision 2.0 MWhets (is that what he said ? Mwhets ?)
)	  Double           1.2

Did it say how this was set up? What I mean is, is it a 680x0 peripheral
or is it running it's own code memory (probably). If it needs it's own
special memory, like cache, then you might as well build a seperate board
and do it up as black box math server. If you are going to go to that
much trouble, might as well go with the '860 and get REAL speed.
I guess I define co-processor as a transparent hardware accelerator.
If you can hook it up to the main processor, with minimum amount of
hassel, and have it run out of processor memory space, then it's a 
co-processor. My definition. Weitek would probably disagree.

)How do these figures compare with '881/2 and 860 ?

I have no clue. I looked in the 881 manual and couldn't find the performance
figures.

)Some interesting stuff about this part - it doesnt exist. It seems
)Weitek has a nice math chip, the 3116 or something like that. They
)sell a daughtorboard that has some glue logic and this chip
)for use with the 386. What they have for the 68000 is a board
)that uses the 3116 and some glue.

Is it compatable with the 881 instruction set? If not, why bother? You'ld
have to write your own compiler for it. YECHH. Unless it does sin(x)/cos(y)
in two cycles...

)Every time I pumped him for information, he pumped me
)wanting to know how many i needed, so thay could make their 
)projections and deicide to make this chip or not.

Should have asked for a sample ;-)

)Hell, I told 'em 10,000. Couldnt hurt. Weitek is in Sunnyvale.

Gee, I can pick one up on my way to work!

)richard@gryphon.COM  decwrl!gryphon!richard   gryphon!richard@elroy.jpl.NASA.GOV

I don't like Weitek. When I was at Raster Tech. I talked to a few of the
engineers that had worked on previous projects involving their 64 bit
FPU/IU chip set. I heard nothing but horror stories about hardware bugs
and instructions that didn't work as advertized. Abort and stall are good
examples.
-- 
Steve -Raz- Berry      Disclaimer: I didn't do nutin!
UUCP: sun!kilowatt!raz                    ARPA: raz%kilowatt.EBay@sun.com
"Fate, it protects little children, old women, and ships named Enterprize"