David Blackman wrote:
> >SSL is, as far as I understand, highly floating-point intensive, as it
> >must (typically) calculate RSA algorithms in software. The Alpha chip
> >should excel in this area. But not by an order of magnitude.
>
> RSA algorithms involve large integer calculations, not floating point. I
> haven't looked at the large integer code in SSL. I have looked at
> old code by Lenstra and Manasse. It used no floating point in the
> inside loops. It did a floating point divide in the next loop out of some
> routines, but i don't think those were the ones needed by the RSA
> algorithm. I have also helped implement a large integer arithmetic library
> that used no floating point operations at all and performed well. I can't
> figure out how to make heavy use of floating point in the RSA algorithm.
You're right, of course. I went and reviewed some of the FAQs from (and
on) RSA - I was remembering one elliptic curve implementation I saw
recently. What I have also seen is a test implementation of RC4 in
assembler using FP on a 16-bit CPU (an i80286+i80287 - don't ask!)
instead of doing things the "conventional" way. I went back and looked
at it again - it is a very, very strange way of thinking.
Sane people, in general, will use large-integer math libraries to
implement RSA. Wherein, I believe, my 50% differential between Intel
and Alpha should be approximately correct, after all.
I thought Intel's FP was not all that bad? I'm not intimately familiar
with the Alpha, but I'd certainly rather use an Intel FPU than AMD or
ARM or ... ...
I know MIPS FPUs are/were generally better than Intel, I don't know
where Motorola stands nowadays. Can you provide any sort of
quantification of the Alpha advantage over Intel in FP domains?
Thank
-Adam
--
Adam Thompson, MCNE, MCSE, CWT, A+
Vice-President / Chief Technology Officer, Commerce Design Inc.
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