The pentium computer chip contains flaws. This is not something new - every computer chip made behaves in this contrary way and there are lists of errata associated with each chip. Serious problems are repaired during various production runs or, if determined early enough, are patched in software.
THE PROBLEM
The Intel pentium problem is technically the same. During the production of some 5 million pentium chips, it was determined that the FDIV instruction gave, for some bit patterns, incorrect results. This affects only floating point calculations, and only for a very few numbers (1728 unique sets of numbers). Floating point division uses a set of lookup tables to speed up calculations. There were/are missing entries in this table, so for some numbers, the answer is incorrect.
Examples:
1)5505001 divided by 294911 is 18.66665197 The pentium answer is: 18.66600093
2)4195835 divided by 3145727 is 1.33382045 The pentium answer is: 1.33373907
Errors could affect the 12th to 16th bits of the number, which means as much as the fourth significant digit.
WHAT HAPPENED
On October 20, Dr. Thomas R. Nicely of Lynchburg College, working on prime numbers, posted a message to CompuServ that he had obtained erroneous results working on a Pentium computer. Intel developed a "white paper"in which they acknowledged the error, but calculated that it was very unlikely to occur (1 in 9 billion random divides), and that they stood behind their processor. A telephone number was setup to screen people who requested a replacement chip for their computer. Customer-support people would ask questions about the kind of computing the people were doing and determine if they would encounter the pentium bug. Intel quickly found out that people doing modeling and statistics complained that they had to fight for a new chip, and one rejected individual commented he hoped that Intel people didn't mind flying on airplanes for which he was designing wings. Another individual reported that he had the support person almost convinced until he mentioned that he was a student. Immediately, the answer was "Replacement not needed." Further complications ensued. IBM, who sold pentium chips, stated that they would stop selling pentiums and produced calculations that the frequency of errors was 100 times higher than Intel suggested. Apple, who sold a Pentium chip competitor, declined to comment. Business Week magazine gave Intel's customer relations decisions second place in their "dumbest moves of 1994." Intel modified their stand. Now, anyone who wanted a new processor would get one. Since there were more than 100 different pentium chips (some with heat-sinks, some with fans, et al), the customer support people would now help to determine the right chip. Intel would also be happy to send an Intel service representative to the computer to install the chip - taking longer, but insuring proper installation.
MCSC RECOMMENDS
If you bought a computer with a pentium chip from us, call us and we will advise you individually. Otherwise we suggest that if you do repeated calculations or statistics or other sensitive engineering mathematics, you should contact Intel as soon as possible. Have the manufacturer's name, serial number and specifications (owners manual and sales slip) of the computer to help determine the correct replacement. Remember you may have to redo all calculations including those that you do while waiting for the chip, so time is urgent. Intel will ask for a credit card number as security that you will return the old chip within 30 days. If time is not urgent, you may decide to wait for a technician, to avoid possible damage to the computer or the consequences of installing the wrong chip. Even if you aren't concerned about the math error because you just do word processing, you should upgrade because you don't know how the computer will be used in the future, or to whom you might sell it.
MORE INFORMATION?
Pentium FAQ: ftp://www.isi.edu/pub/carlton/pentium
Electrical Engineering Times: http://www.wais.com/techweb/eet/current/hr.html
Intel Customer Support:
http://www.intel.com/product/pentium/cpuidf.exe ftp://ftp.intel.com/pub/IAL/pentium/cpuidf.exe and cpuidf.txt
The MathWorks, Inc.: http://www.mathworks.com/Pentium/README.html
Richard Beck MCSC Support Specialist