[RC5] oddball DES vs. CPU speeds

Joe Zbiciak j-zbiciak1 at ti.com
Tue Jan 20 07:01:20 EST 1998


'Svend' said previously:

| > And then the Windows 95 speed puzzles me. On my 120 MHz Pentium the
| > client runs at above 600 K key/second in Windows NT, but only at about
| > 550 K keys/second in Windows 95. I don't know the current plans, but I
| > could consider looking into this. One possible solution could be to
| > make a version, which has a slightly lower maximum speed, but runs in
| > less memory and might be less sensitive to conditions in Windows 95.

There's another detail, in that Win95 supposedly heavily pollutes the
cache relative to WinNT, even when idle.  So, if the core touches alot
of memory or is large, it may run noticibly slower under Win95 on the
same hardware.  A "lite" version which was not as heavily unrolled may
fare better under Win95.
 
'Remi Guyomarch' said previously:

| There could be a significant difference between a 'standard' Pentium
| with 2x16 KB cache versus a MMX enhanced Pentium with 2x32 KB cache.
| Have you an estimate of the code+data space your core is using in its
| internal loop ?

Also, MMX Pentiums have relaxed some of the instruction-pairing 
restrictions as well.  (I believe Eric Gindrup posted some of the
Intel tech notes on the subject.)  Any reasonable comparison between
the client running under Win95 and under WinNT should probably 
occur on the exact same machine.  


Regards,

--Joe

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