Re: i686 quirk for AMD Geode

H. Peter Anvin
2009-11-08T22:17:34Z

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Keep in mind that if we end up running that on code with any kind of significant fraction of CMOV it will utterly suck. Count 500-odd cycles per emulated instruction. It *is* still useful in some cases - which is why we have x87 emulation already, for example. The question is mostly where the point of diminishing returns go. In theory we could provide a full x86 interpreter (perhaps shared with KVM?) which would allow any instruction at all to be executed.

"Alan Cox" <alan@lxorguk.ukuu.org.uk> wrote:

>> > Better to be sure that a NOPL whouldn't SIGILL your program, isn't
>> > it?
>>
>> SIGILL is easier to debug than NOPL mysteriously taking 100x time it
>> should, sorry.
>
>And a working 686 distribution is a great deal more useful to end users,
>who outnumber you by a few million to one. It's a very sensible patch, or
>perhaps you'd prefer we didn't say. And you forget the user "debug" for
>a Geode + i686 without this will be "it hangs when I try and boot the
>install CD"
>
>It would probably also be worth having cmov fixups for the VIA C3 as well.
>
>Alan

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