*BSD News Article 8465


Return to BSD News archive

Path: sserve!manuel.anu.edu.au!munnari.oz.au!news.hawaii.edu!ames!olivea!uunet!kithrup!sef
From: sef@kithrup.COM (Sean Eric Fagan)
Newsgroups: comp.unix.bsd
Subject: Re: [386bsd] installing fpu (ULSI) results in floating exceptions
Message-ID: <1992Dec01.215405.11060@kithrup.COM>
Date: 1 Dec 92 21:54:05 GMT
References: <ByJIpL.69w@unx.sas.com> <1992Nov30.190622.2701@kithrup.COM> <1992Dec1.124507.10959@ponds.uucp>
Organization: Kithrup Enterprises, Ltd.
Lines: 20

In article <1992Dec1.124507.10959@ponds.uucp> rivers@ponds.uucp (Thomas David Rivers) writes:
> There *are* apparently
> some instructions available on a INTEL (or Cyrix since it's basically
> the same mask) 80387 with which the ULSI part doesn't function.

That is *not* what you said.  You said that it would execute *only* the '387
instructions, and *not* the instructions common to both '287 and '387.

If the chip were a '287 in a '387 pinout, I would not be surprised at all.
And, yes, that could lead to some problems if programs make indiscriminate
use of the '387 instructions.  (SCO's libc and libm, for example, check to
see what the fpu type is, and execute one of three different cos() etc.
routines depending on the result.  If, however, the chip is really a '287
but says it's a '387, that wouldn't work, of course.)

-- 
Sean Eric Fagan  | "we will probably just crash immediately; but at least
sef@kithrup.COM  |  we will have written less code."
-----------------+                 -- Chris Torek (torek@ee.lbl.gov)
Any opinions expressed are my own, and generally unpopular with others.