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SubjectRe: Linux support for Intel MMX CPU's
Date
In article <Pine.LNX.3.94.960816181143.20286C-100000@vci.vistacom.fi>,
=?ISO-8859-1?Q?Johan_Myr=E9en?= <jem@vistacom.fi> wrote:
>On Fri, 16 Aug 1996, Michael Mansour wrote:
>
>> During 1997, MMX will be released by Intel with their CPU's, I am
>> wondering whether Linux will be able to take advantage of these advanced
>> multimedia capabilities at chip level? Will it be kernel support or app
>> support or both?
>
>The kernel itself does not need multimedia capabilities, but I'm sure some
>kernel hacker with a sufficiently twisted mind (especially Linus himself)
>can come up with some interesting uses for the new instructions in the
>kernel code :-)
>
>Other than that, MMX is purely a user level thing. Applications can start
>using the new instructions and be happy. No kernel support is needed
>(except perhaps for /proc/cpuinfo). The MMX registers map to the FPU
>registers, so no new registers need to be saved on context switch.

Linus mentioned that task switching used tricks to be lazy about
FPU state saving. I can't find the relevant code right now. Maybe
somebody should check that these MMX instructions don't bypass
whatever method Linux uses to trigger a forced save of FPU state.

--Malcolm

--
Malcolm Beattie <mbeattie@sable.ox.ac.uk>
Oxford University Computing Services
"Widget. It's got a widget. A lovely widget. A widget it has got." --Jack Dee

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