There's memory bandwidth and there's memory transaction thruput

johnm at johnm at
Sat Feb 13 17:55:33 UTC 1999

Thanks for the informative message, Jan.

I've long wondered why Squeak runs better on some processors
than others. Some of the surprises have been:

  1. it runs surprisingly slowly on the PPC 603 (due to small L1 caches?)
  2. it runs surprisingly fast on the PPC 750 (G3) (good job, Tim Olson!)
     (due backside L2 cache and short pipepline?)
  3. it runs a bit slower than one might expect on Pentium processors,
     compared with PPC (this could be due to lots of things, including
     a mediocre compiler, poor register utilization, or the deep pipeline)
  4. it runs really slowly on 386/486 and 68K machines
     (almost certainly due to insufficient registers)
  5. it runs very poorly on Pentium machines that lack L2 caches

I'd love it if someone who really understood modern processors could
suggest ways to improve Squeak's performance!

	-- John

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