-----BEGIN PGP SIGNED MESSAGE----- NASIRC BULLETIN #94-36 December 13, 1994 Floating Point Divide Flaw in Intel Pentium Processor Chip ============================================================ __ __ __ ___ ___ ____ ____ /_/\ /_/| /_/ / _/\ /_/| / __/ \ / __/\ | |\ \| || / \ \ | /\/ | || | /\ \/ | | \/ | ||\ \ || / /\ \ \ \ \ | || |_\/ /\ | | | || \ \|| / /--\ \ \ /\_\\ | || | |\ \ \ | \_/\ |_|/ \_|//_/ \_\/ \/__/ |_|/ |_| \_\/ \___\/ NASA Automated Systems Incident Response Capability ============================================================ 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. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= 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. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= =============================================================== For further assistance, please contact the NASIRC Helpdesk: Phone: 1-800-7-NASIRC Fax: 1-301-441-1853 Internet Email: nasirc@nasa.gov 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 docserver@first.org with an empty "subject" line and a message body containing the line "send first-contacts". ************************************************************************* * Richard K. Yamane Leeward Community College * * Manager, Computer Center 96-045 Ala Ike * * Pearl City, Hawaii 96782 * * EM: sysrich@lccada.lcc.hawaii.edu * * Ph: (808) 455-0493 (Univ. of Hawaii campus) * ************************************************************************* ************************************************************************** *Marv Weissman * UH Computer Specialist * Leeward Community College * *cs_weissman@lccada.lcc.hawaii.edu (808)455-0465, voice. 455-0471, fax * * * * "Don't worry about what may happen tomorrow; just correct what you * * spoiled yesterday" * * * * (Midrash ) * * * ************************************************************************* - --- [This message has been signed by an auto-signing service. 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