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Intel confirms Pentium "F0" bug

The chipmaker says it is looking into a work-around for a bug that can freeze up Pentium MMX and "classic" Pentium computers.

Brooke Crothers Former CNET contributor
Brooke Crothers writes about mobile computer systems, including laptops, tablets, smartphones: how they define the computing experience and the hardware that makes them tick. He has served as an editor at large at CNET News and a contributing reporter to The New York Times' Bits and Technology sections. His interest in things small began when living in Tokyo in a very small apartment for a very long time.
Brooke Crothers
2 min read
Intel (INTC) today confirmed that a bug can crash its Pentium processors, and the chip giant was rushing to come up with a fix.

Intel acknowledged the "F0" bug this afternoon, saying that it is now looking into a work-around. A spokesperson said the company would know more about the work-around "within a week."

Though completely different in nature, the F0 bug evokes memories of a calculation glitch in the Pentium found by a mathematics professor back in 1994, which cost Intel close to $500 million dollars.

"Yes, we are confirming this is an errata. This was not on our published list of [processor bugs]. We didn't know it existed until Friday," the spokesperson said today.

Intel publishes a list of Pentium, Pentium Pro, and Pentium II bugs. These problems, referred to as "errata," are supposed to cover all known bugs.

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

The Pentium F0 bug affects Pentium MMX and "classic" Pentium (non-MMX) computers, machines that number in the hundreds of millions worldwide.

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 re-started.

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.

Intel confirmed that the bug occurs only when the processor receives an illegal, one-line instruction. "The result is the system could freeze," Intel said.

"This bug will not be found in commercial software," Intel added. The bug does not affect Pentium Pro or Pentium II processors.

Nathan Brookwood, an analyst at marketing research firm Dataquest, said the bug is similar to glitch found in the IBM 790 computer back in the early 1960s. In that case, a single errant instruction was able to bring down an IBM computer.

"This is dangerous if you're in a multiuser environment. If somebody does it to himself, fine. I don't care. But if somebody takes a bomb onto a plane I'm flying on, then I care," he said.

One interesting aspect of the bug is that, in the case of a system crash, the processor is actually still running. This may allow Intel to "discover the state" of the processor and thereby come up with a software fix, Brookwood said.

"They may be able to set up an error-handling condition...That's what they are working on now within Intel and with key operating system suppliers," he said.

Brookwood said the strategy will probably be to go to operating system vendors and say, "Here's the problem and here's the work-around, and go figure out how to implement it."