Path: utzoo!attcan!uunet!husc6!rutgers!njin!princeton!phoenix!caromero
From: caromero@phoenix.Princeton.EDU (C. Antonio Romero)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 80386 versus 80387
Keywords: 80386, 80387, 80287
Message-ID: <8389@phoenix.Princeton.EDU>
Date: 12 May 89 16:47:50 GMT
References: <1427@uw-entropy.ms.washington.edu>
Reply-To: caromero@phoenix.Princeton.EDU (C. Antonio Romero)
Organization: Princeton University, NJ
Lines: 37

In article <1427@uw-entropy.ms.washington.edu> joe%uw-evolution@entropy.ms.washington.edu writes:
>I have heard that there is a sporadic nasty interaction between 80386's
>and 80387 numeric co-processors, owing to a design flaw in the 80386,
>and that it is not cleared up yet....
> (I happen to be using Unix, but if this is the problem that
>may be irrelevant).

I'm not 100% sure that the problem you're having is the one I'm thinking
of, but as I recall there was a floating-point problem that plagued
early 386 machines, which did show up when using unix.  I believe
operating system paralysis under Unix as you describe was the symptom.

To my knowledge this has been corrected as of a couple of years ago.
If you've had your machine that long, you may just need a new 386
chip.  The new chip has a double-sigma stenciled on it somewhere; the
old chip has, I think, just one sigma, or no markings at all.

(I had to check my father's machine out under Xenix to make sure it had
the newer chip-- he got one of the relatively early Compaq 386's,
before 20MHz etc. was ready.  It did have a new chip, so I never saw the
problem actually occur; but the symptoms as described to me sound like
what you're running into.)

Who knows?  Maybe you can badger Zenith into sending you a new 386 chip,
if you're nasty-- err, insistent enough about it... ;)

Also, a 287 won't just drop in unless the Zenith is designed to handle
one... (having never popped the top on a Zenith I don't know if it is).

>Question: are there 80287's fast enough to work with a 16 MHz 80386
>(I think the answer is yes)?

Many machines early on (and even now, I think) can accomodate a 287.
I believe the faster 287 part exists, but I don't think using it will
solve your problem.

-Antonio Romero      romero@confidence.princeton.edu