Flawed AMD Chip Can Lead To Data Corruption

Brandonski writes "Apparently AMD allowed some flawed chips to slip through their detection grid. The problem affects only a small number of chips and only single core 2.6 and 2.8 GHz CPUs." From the article: "It is believed that the glitch is triggered when the affected chip's FPU is made to loop through a series of memory-fetch, multiplication and addition operations without any condition checks on the result of the calculations. The loop has to run over and over again for long enough to cause localized heating which together with high ambient temperatures could combine to cause the result of the operation to be recorded incorrectly, leading to data corruption."

Comments

Re:Kernel fix?

[larry bagina]

I'm sure someone will have a kernel patch to prevent this from happening in linux in very short order.

Not likely. This is valid user code that is being executed. On other CPUs, the same code wouldn't cause a problem. Something like the F00F bug is fixable in the kernel by mucking with exception handler. This is pure user-land code.

Re:An old problem

[Mister Transistor]

You may be referring to the early MC6800 8-bit processors. The first ones had a major problem in that the internal registers were dynamic RAM style memory, and synchronized to the internal state clock. If you halted the processor for an extended period of time, the refresh clock to them ceased and the registers got hot, drew too much current and burned up!

I'm pretty sure that gave rise to the joke "Halt and Catch Fire"...

I always figured that if you were to burn out a register from overuse, it would be the carry bit ;)

Anyway, as to the story at hand, it sounds like this would only ever occur a) to only 3000 processors total - MAYBE, and b) would only ever happen under such an artifically contrived laboratory stress-test/benchmark situation. Any CPU running in a real system would a) have to do other things like service hardware interrupts, and b) wouldn't do something useless like perform a looping calculation without checking to see if it was done periodically. It really sounds like this is a big non-issue in reality.

Re:An old problem

[something_wicked_thi]

RTFA. They are offering a free replacement. However, the FDIV bug was overblown. For most people, it didn't matter (few people were using software that required division precise enough to be affected). This bug is even less worrisome. Its effect is, at the moment, completely unobserved in the wild using real world applications. The FDIV bug was apparent to anyone with a calculator.

I'm not saying AMD should be let off the hook completely, but the bug isn't a big problem, they are offering free replacements, and they publicized it. The FDIV bug was bigger (though still hardly catastrophic), refused (at first) to offer replacements, and they sat on it. The two scenarios are nowhere near similar. Maybe AMD just has more character than Intel, or maybe they were watching in 94/95 when the FDIV bug happened and they've actually learned from Intel's mistakes. Regardless, this whole story is more of a heads-up to concerned buyers than a criticism of AMD.