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Intel releases Pentium bug fix

Intel releases software to fix a flaw affecting Pentium and Pentium MMX computer chips.

Intel (INTC) released a software work-around for the Pentium "F0" bug, which affects Pentium MMX and Pentium "classic" (non-MMX) microprocessors.

Having confirmed the bug's existence earlier this week, the chipmaking giant today described how operating systems can be configured to prevent crashes caused by the bug's illegal instruction.

Major operating system vendors such as Microsoft and IBM simultaneously released statements describing the bug's possible affects on their products.

The bug was first reported by CNET's NEWS.COM last Friday. Intel is an investor in CNET: The Computer Network.

A computer affected by the bug stops operating--a so-called freeze-up. A "ctrl-alt-delete" keyboard operation, which can generally be used for "rebooting" a computer, will not work. The computer must be restarted.

The bug should not affect ordinary computer users since the offending instruction is not something that appears in software that people install on their PCs. Someone has to intentionally and maliciously execute a program with this instruction on a computer.

Today, Intel stated the following about the bug.

"The ['F0' bug] affects the Pentium processor, Pentium processor with MMX technology, Pentium OverDrive Processor and Pentium OverDrive processors with MMX technology.

"It does not affect the Pentium Pro processor, Pentium II processor and i486 and earlier processors.

"This invalid instruction is not in commercial software.

"The erratum only occurs when the processor receives a specific invalid instruction. The result of this erratum is the system may 'freeze' and would have to be turned off and rebooted to return to normal operation.

"We have identified a workaround that prevents the system from being 'frozen' by this invalid instruction and allows it to continue normal operation. The workaround modifies the execution flow to avoid the system hang after the invalid instruction is received. The workaround can be implemented through the operating system software."

Intel described the workaround as follows.

"Intel has been working with industry operating system vendors to assist them in implementing this workaround for their operating systems. Users should contact their operating system vendor for specific availability of the workaround for that OS."

Vendors made the following comments.

"[Microsoft is] in the process of studying the implementation of potential workarounds in order to meet the needs of our customers," said Moshe Dunie, vice-president of the Windows Operating Systems Division. "Since this erratum can only be exploited by a program that was developed with malicious intent and deliberately uses this illegal instruction, following common-sense computing practices, such as not downloading or running executables from unknown sources, can protect a user from this problem."

"In response to the invalid instruction erratum confirmed Monday (11/10/97) by Intel, IBM and Intel are working together to deliver a software workaround for OS/2 users to the processor erratum. The erratum, under certain user-definable conditions, can affect Intel Pentium Processor and Pentium Processor with MMX Technology systems running any operating system, including IBM's OS/2. Once testing is completed, the workaround will be made available to OS/2 customers."