[geeks] RC5 on old machines

[Dave McGuire]

On December 13, Kris Kirby wrote:
> IPX, 40MHz stock: 31.430 - 31.665 kkeys/s
> IPC, 25MHz : 18.609 kkeys/s
> 
> Comparison:
> 166MHz [1] P54C: ~220 KKeys/s
> 90MHz Pentium: ~100 KKey/s
> 75MHz K5: ~200 KKeys/s
> 300MHz K6/2: ~540 KKey/s
> 433MHz dual Celeron: 2.39 Mkey/s, 1.195Mkey per processor
> 850MHz K7: 2.41 Mkeys/s
> 
> Nexgen P90 [2]: ~16 KKeys/s
> 
> [0] Doesn't appear to be stock; looks like a Wietek chip.
> [1] Non-MMX
> [2] No FPU, but is a RISC chip running a i386 emulator.

  I didn't see anything tagged with a [0] above, but if you're talking
about one of the SPARCstations, Weitek made a lot of SPARC-related FPU
chips.  In those instances, having a Weitek label doesn't mean they're
upgrade chips of any sort.

  Also...one cannot use this disparity in RC5 performance as any sort of
speed comparison, because the intel-architecture processors have
instructions that make RC5 whiz by at substantially greater speeds
than most other processors.  PowerPC processors also have those
instructions.  Since typical workloads don't use those instructions
very much, this performance gain isn't seen across a wide range of
applications...which is why an older SPARCstation will do a LOT more
work than an older (and a lot of newer) PeeCees.

  Specifically, the instructions in question are bit rotates.
Interestingly, Intel (in their infinite processor-design wisdom, cough
cough) badly crippled their P4 processors for some strange reason
(increase clock rate at any cost?)...so a P4 runs RC5 at about half
the speed of a P-III at the same clock rate.  Also at the same clock
rate, a PPC G4 runs RC5 at three times the speed of a P-III...or SIX
TIMES the speed of the whiz-bang P4 at the same clock rate.

  Another interesting statistic about the P4 from distributed.net is
that the P4 runs RC5 at EXACTLY the same speed (same number of clock
cycles per key) as the original Pentium at the same clock rate.

  Since a lot of PeeCee weenies seem to benchmark their machines using
RC5, I find this interesting.

        -Dave

-- 
Dave McGuire
St. Petersburg, FL