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something NOT MIME-related
Hello:
Not to distract from the entertaining MIME thread, but I've got a
question that's a little closer to a crypto topic (i.e., software
psueudo-random number generators).
In the aftermath of the Pentium-can't-divide-accurately flap, I modified
a random-number generation routine I'd written to check for the presence
of the Pentium divide errors. In the process, I put in a routine that
did an elementary benchmarking of the chip's performance in both integer
(speed to repeatedly execute an empty for-loop 1 million times) and floating
point operations (inserting a divide operation in the loop, and adjusting
the resulting execution time by subtracting the time required for the
empty loop before computing divide-calculations-per-second performance).
This is an admittedly very crude benchmark, but I wanted to get some
rough idea how many divides could be performed per minute of program
execution (i.e., to estimate how long the program could run before a
Pentium-problem might occur).
Anyway, I found what appeared to be very strange results when
comparing performance on my 486/66 versus a 486/25 and 386/20: namely,
although the 386 was dead last on both the primarily integer-based empty-
for-loop and for-loop-with-divide timings, the 486/25 and 486/66 turned
in effectively identical times in the empty-loop benchmark (the 486/66 was
about 33% faster than the 486/25 in the divide-based benchmark). All
machines were running essentially equivalent versions of Windows for
Workgroups).
My question is, why would the 486/66 and 25 produce comparable integer-
based empty loop performance? I haven't tried a comparable program running
under plain-DOS to see if this is somehow Windows related. I supsect there's
an easy explanation, but it escapes me. Any suggestions would be greatly
appreciated.
rj
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R. J. Harvey (mail: [email protected])
(PGPkey 0BADDDB5: 82 42 53 EA 97 B0 A2 B2 FC 92 90 BB C2 26 FD 21)