06 March 2012, 14:55

DragonFly BSD developer finds hardware bug in several AMD CPUs

AMD Phenom II Processor Matthew Dillon, founder and main developer of the DragonFly BSD project has uncovered a hardware bug in several AMD processors. Dillon received confirmation from AMD that a bug he had found in the CPU's fill_sons_in_loop code last year does indeed lead to segmentation faults under certain conditions.

Dillon worked with engineers from AMD over several months to duplicate the bug which he had first discovered while working on DragonFly BSD. In the process, he designed a test case USB image of DragonFly BSD that AMD used to track down the bug. It turns out that the problem affects the AMD Opteron 6168 and Phenom II X4 820 processors, albeit only under very specific conditions when the CPU updates the stack pointer.

AMD has said it will update the documentation for the affected processors, enabling developers to avoid this unwanted behaviour in the future.

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