AMD cpu bug update -- AMD confirms!
dillon at apollo.backplane.com
Mon Mar 5 11:27:44 PST 2012
AMD has confirmed the cpu bug that I analyzed. I am going to quote
the first paragraph. They gave me some more info and will be updating
their revision guide. To avoid any confusion (so they can finalize their
wording for the entry they will be putting in the revision guide) I'm
just including the confirmation here.
"AMD has taken your example and also analyzed the segmentation fault and
the fill_sons_in_loop code. We confirm that you have found an erratum
with som e 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
We exchanged a few emails to try to come up with a good test case.
Owing to the difficulty of reproducing the bug I constructed a
fully bootable DFly operating system & test case USB image and
verified that the bug was present on my test box using that image.
AMD was then able to reproduce the bug using that image on their own
machines. Over the last few months they have been working through
the possibilities and today emailed me the confirmation that it was,
indeed, a cpu bug.
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 at backplane.com>
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