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Re the Pentium Bug
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NASIRC BULLETIN #94-36 December 13, 1994
Floating Point Divide Flaw in Intel Pentium Processor Chip
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NASA Automated Systems Incident Response Capability
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NASIRC has become aware of a floating-point division problem in some
versions of the Pentium processor chip, manufactured by Intel. Although
this is not a security issue, NASIRC is bringing this to your attention
because the defect could cause erroneous results for NASA projects which
rely on complex mathematical computations involving double-precision
arithmetic.
Information on this problem is currently being propagated through the
Internet and both technical and general publications. We are issuing this
bulletin to provide a synopsis of what is known about the problem, how to
check for the flaw, and what to do about it.
It is important that any individual who uses a computer utilizing a
Pentium processor perform the test(s) described in this bulletin on
his/her machine to check for the bug. Although there have been reports
the Pentium/60 is not affected, NASIRC recommends these units also be
tested.
There is no part number or other marking which would designate the flawed
processor chips from the later revisions, which do not contain the bug.
Intel considers this flaw to be minor, and has stated: "the average
spreadsheet user should only be affected by this bug once every 27,000
years". However, NASIRC feels there is a high probability that work done
on this class of desktop system in NASA is most likely to be
computationally intensive, and the likelihood of achieving erroneous
results is strong. From a reliability and reputation standpoint, NASA must
ensure that the tools it uses to accomplish its mission perform properly.
The president of Intel has issued a communique, stating his company's
position on the problem, and the the process to follow should a site
discover a flawed system. The communique is available via WWW at the
URL: http://www.intel.com/about-intel/press/andy-msg.html.
Pentium machines can be tested by using any of the following three
methods:
1) Using the Microsoft Windows calculator, perform the following
computation:
x = 4195835
y = 3145727
z = x - (x/y)*y
If z = 256, your chip has the bug. The Windows calculator is the
easiest way to run this test. If you program this calculation, be
sure to use to use double-precision variables!
2) Using any spreadsheet application (Lotus 1-2-3, Excel, etc), perform
the following test:
Enter the following data:
In cell A1: 4195835
In cell A2: 3145727
In cell A3: 3145727
Calculate the following value:
(A1 * A2)/A3
A correct result is: 4195835
An incorrect result (FDIV bug) is: 4195579
3) A small program named P87TEST.COM, to test for the existence of the
bug was written and made available over the Internet by Terje
Mathisen of Norsk Hydro A/S in Norway.
A binary copy of P87TEST.COM can be obtained via anonymous FTP from
the NASIRC online archive at the following URL:
ftp://nasirc.nasa.gov/toolkits/diagnostics/Intel/p87test.com
The Checksums are as follows:
MD5: 322E8857C126D7CA336E7FFC31800939
SunOS: 08334 2
To run the program, simply type: P87TEST. An example of the
program output is as follows:
Pentium FDIV bug finder. (c) Terje Mathisen 1994
This is a Pentium or better cpu
CPUID reports back:
Vendor id = "GenuineIntel"
Family (4=486, 5=Pentium etc.) = 05, stepping = 05, model = 01
CPU feature list:
1 : FPU (NDP) onchip
2 : Virtual 86 Mode Extensions
4 : I/O Breakpoints
8 : Page Size Extensions
10 : Time Stamp Counter
20 : Pentium stype MSRs
80 : Machine Check Exception
100 : CMPXCHG8B instruction available
It has a 387 or later ndp
It has the FDIV bug:
(1.0/824633702449.0)*824633702449.0 is not equal to 1.0!
Intel has stated that any site experiencing problems from this bug
can obtain a replacement processor chip at no charge.
Intel has set up a special customer service phone number for users
affected by this bug. The Intel customer service desk can assist
with obtaining replacement processor chips for affected systems.
Any site confirming the existence of the bug in their Pentium chipset
should contact Intel at 1-800-628-8686.
If you have any questions about this bulletin, please contact the
NASIRC Helpdesk.
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NASIRC ACKNOWLEDGES: Mr. Bob Solomon of the NASA Lewis Research
Center for providing the information used in this bulletin,
and Mr. Terje Mathisen of Norsk Hydro A/S for creating the pro-
gram to test a system for the bug.
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For further assistance, please contact the NASIRC Helpdesk:
Phone: 1-800-7-NASIRC Fax: 1-301-441-1853
Internet Email: [email protected]
24 Hour/Emergency Pager: 1-800-759-7243/Pin:2023056
STU III: 1-301-982-5480
===============================================================
This bulletin may be forwarded without restriction to sites and
system administrators within the NASA community.
The NASIRC online archive system is available via anonymous ftp.
You will be required to enter your valid e-mail address as the
"password". Once on the system, you can access the following
information:
~/bulletins ! contains NASIRC bulletins
~/information ! contains various informational files
~/toolkits ! contains automated toolkit software
The contents of these directories is updated on a continuous
basis with relevant software and information; contact the NASIRC
Helpdesk for more information or assistance.
-----------------
PLEASE NOTE: Users outside of the NASA community may receive NASIRC
bulletins. If you are not part of the NASA community, please contact
your agency's response team to report incidents. Your agency's team
will coordinate with NASIRC, who will ensure the proper internal
NASA team(s) are notified. NASIRC is a member of the Forum of
Incident Response and Security Teams (FIRST), a world-wide organiza-
tion which provides for coordination between incident response teams
in handling computer-security-related issues. You can obtain a list
of FIRST member organizations and their constituencies by sending
email to [email protected] with an empty "subject" line and a
message body containing the line "send first-contacts".
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* Richard K. Yamane Leeward Community College *
* Manager, Computer Center 96-045 Ala Ike *
* Pearl City, Hawaii 96782 *
* EM: [email protected] *
* Ph: (808) 455-0493 (Univ. of Hawaii campus) *
*************************************************************************
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*Marv Weissman * UH Computer Specialist * Leeward Community College *
*[email protected] (808)455-0465, voice. 455-0471, fax *
* *
* "Don't worry about what may happen tomorrow; just correct what you *
* spoiled yesterday" *
* *
* (Midrash ) *
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