[rc5] Why are Alpha's so much slower then wintel boxes?

Eric Leblanc jughead at generation.net
Fri Oct 31 18:30:34 EST 1997


Dan Sugalski wrote:
> 
> At 03:13 PM 10/31/1997 -0600, Brian Greul (Exch) wrote:
> >Does anyone have any ideas on why Alphas might be so much slower than
> >wintel boxes at crunching this code?
> >I would expect them to perform on par.
> 
> That, alas, turns out not to be the case. The Alpha processor doesn't have
> a rotate instruction, so it's gotta be faked by the code. This, needless to
> say, slows things down, so you end up with less than stellar numbers.

If you want the biggest bang for your idle cycle using the Alphas. I
suggest you take a look at finding Mersenne prime. The test used uses
exclusively the FPU comparatively to rc5 which use integer arithmetics.

Myself, i'm at the opposite of the spectrum. My K6 is so slow in FPU
operation compared my Intel Pentium.

Look at http://www.mersenne,org/prime.htm for more info on the mersenne
project.


-- 
Eric Leblanc
------------
email : jughead at generation.net
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