[LinuxBIOS] Intel microcode revision code

joe at smittys.pointclark.net joe at smittys.pointclark.net
Wed Dec 12 13:33:13 CET 2007

Quoting Martin.Karlsson at emerson.com:

> Hello,
> Yesterday I wrote some code for the Syslinux boot loader that is meant
> to boot different images based on which revision of the CPU microcode
> that is currently loaded in the CPU (yes, this is a bit strange but we
> have a very good reason for it). I then compared my implementation with
> a few others an ran across yours, in
> http://www.openbios.org/viewvc/trunk/LinuxBIOSv2/src/cpu/intel/microcode
> /microcode.c?view=markup
> Question to you guys: why is the first wrmsr instruction there? From my
> understanding, by not properly initialising ECX, EAX and EDX this will
> overwrite whatever is in the MSR pointed to by ECX?!
> BTW I tried out your code on our target hardware (Intel Celeron M, 600
> MHz) and with that first wrmsr line in place it hangs and without it, it
> runs just fine.
> Just wanted to let you know.
> Best regards,
> Martin Karlsson
Hmm, very good question. I think the microcode has been waiting for  
sommeone to update it. Anyone else have a take on this?

Thanks - Joe

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