AMD confirms CPU bug
AMD has confirmed a CPU bug that means processors could make errors under specific conditions.
The bug was discovered by Matt Dillon of OS developer DragonFly BSD, who found that code failed to properly execute in certain circumstances.
Dillon outlined the issue late last year after coming across faults during operating system development, and found that the problem only showed up on AMD machines.
He has since been working with the chipmaker, which he says has confirmed in an email that the problem was genuine.
“AMD has confirmed the CPU bug that I analysed,” he wrote in a blog post. “I’m pretty stoked… it isn’t every day that a guy like me gets to find an honest-to-god hardware bug in a major CPU.”
Dillon went on to quote an email from AMD, although he said he was omitting details to allow the company to get its official response in order.
“AMD has taken your example and also analysed the segmentation fault and the fill_sons_in_loop code,” AMD wrote. “We confirm that you have found an erratum with some AMD processor families.
“The specific compiled version of the fill_sons_in_loop code, through a very specific sequence of consecutive back-to-back pops and (near) return instructions, can create a condition where the process or incorrectly updates the stack pointer.”
According to Dillon, proving the bug’s existence required writing a special fully bootable version of the Dragonfly OS to verify the problem.
The news comes a day after the company announced it was giving up its stake in GlobalFoundaries, the manufacturing business it spun off three years ago.
AMD had previously used GlobalFoundaries as its main manufacturer, but has cut its involvement in the company and finally sold its remaining 8.8% stake in the business, leaving it fully owned by the United Arab Emirates Government.
The companies announced a new wafer supply agreement that should allow AMD to use other manufacturers for its 28nm products, and waived various payment obligations that AMD had with the company.
The move allows AMD to be more flexible in the way it chooses manufacturing partners, but will eventually cost the company $703 million, it said.
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