Re: SUMMARY: pentium optimized debian discussion
On 29-Jul-1998, Stephen Zander <gibreel@pobox.com> wrote:
> >>>>> "Joey" == Joey Hess <joey@kitenet.net> writes:
> Joey> If we can clear up the naming problem and people agree with
> Joey> the points in this summary about speed, then I think we can
> Joey> set up the architecture on the ftp site now.
>
> I've sat on one side through all of this but one thing occurs to me:
>
> Waht, if any, difference do the MMX instructions make? My IBM 760XL
> laptop (166MHz MMX) reports 330.96 bogo-mips & I've always presumed
> that MMX was responsible. Does pegcs/egcs -mpentim support the MMX
> instructions yet?
MMX makes no difference for most users.
The MMX CPU was cunningly shipped with a larger L1 cache, so it was
always going to be faster than non-MMX smaller cache pentiums.
The MMX instructions are SIMD instructions (single instruction, multiple
data) -- they perform integer operations on several bytes at a time.
This is useful for some graphics manipulation code and a few other
applications. You need to write special assembly code to do it, it's
pretty difficult for a compiler to take advantage of.
I have heard the AMD-K6-2 has "3d instructions" which as similar, but perform
multiple floating point instructions at once. This is very useful for
some 3d applications (games).
And, what's more, bogo-mips are bogus, so don't rely on them as anything
more than a conversation piece.
Tyson.
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