[RC5] Clocks per Key on Pentium vs PPC604

kmclaurin at akashic.com kmclaurin at akashic.com
Tue Jan 6 13:52:02 EST 1998


Maybe this has already been discussed but I was wondering if there is an 
simple explanation of why the PPC appears to be twice as efficient as the 
Pentium on key processing.

For example, a Pent133 takes 1503 Secs to process 2^28 keys which results in 
744 HzSec (?cycles?) per key while a 120MHz PPC takes 694 Secs for 2^28 keys 
resulting in 310 cycles/key. The P133 is running under W95 and the time is 
taken from Wintop. The PPC is a Mac using OS8 with the time taken with all 
other applications shut down (387kk/sec). The Pentium is using a 6401 client 
while the Mac is using a 6402 version.

 I haven't looked at the internal structure of the 604 and Pentium (54 I 
think) for several years but it looks like the 604 PPC has twice as many 
integer units or 'pipelines' as the Pentium?? Or is there something else 
going on like how many clock cycles it takes to execute an instruction as in 
the 2 Tstates for the Motorola cpu's vs 3 to 5 T states for the Intel/Zilog 
cpus (real old stuff like 6800 vs Z80).



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