Subject: Re: CCL:DEFECTIVE PENTIUM FPU'S

From: [email-masked] (Walter E. Reiher III)
Date: Wed, 23 Nov 1994 12:26:37 -0800 (PST)

Thanks to John McKelvey for informing us of this disturbing problem.

I just took a look at comp.sys.intel to learn more about this problem
with Pentium chips.  There's a lot of flaming going on over there, but
to summarize briefly:
. It looks like some folks (outside of Intel) have known about this
  problem for a couple of weeks now.
  . There are reports of problems with both single- and double-precision
    division.
. Intel has known about it for a while and hasn't told anyone.  They
  have supposedly fixed the problem but did not mark the chips so we can
  easily tell a chip has the fix just by looking.
  . I have not seen a report of anyone who actually has CPU with the fix.
. The problem was reported on CNN yesterday (I didn't see it).
  . Reportedly, an Intel spokesman said on CNN that they will NOT simply
    replace all defective CPUs in the field because they do not consider
    the problem to be significant.  They will replace chips on a case-
    by-case basis.  It looks like THEY will decide if it's important to
    YOU whether floating point calculations are right or wrong in your
    Pentium.
. Some folks have reported success with reaching Intel Microprocessor
  Support at 800-628-8686.  (I haven't tried yet.)
  . A statement attributed to Intel (I can't verify this) said:
    "Concerned users doing extensive floating point operations requiring
    extraordinary precision who desire further details can call Intel at
    408-765-8914."

Terje Mathisen of Hydro Data, Norsk Hydro posted a very small program
which tells you if your system has the problem.  It's pretty obvious...
mine says (sigh):
     "It has the FDIV bug:
      (1.0/824633702449.0)*824633702449.0 is not equal to 1.0!"
He posted his uuencoded program to comp.sys.intel with assembly source.
That message is attached.
     For convenience, I have decoded the program and uploaded the binary
file to ftp.ccl.net/incoming/p87test.zip.  Download it by binary FTP and
use either Info-ZIP's or PKZIP's unzippers to decompress.

Wally
========================================================================
Walter E. Reiher III, Ph.D.                            [email-masked]
Consultant in Computational Chemistry
P.O. Box 61056                                        voice 408-720-0240
Sunnyvale, CA 94088                                     fax 408-720-0378