[rc5] Re: rc5-digest V1 #91

andrew meggs insect at antennahead.com
Thu Aug 21 20:17:57 EDT 1997

James Knowles <jknowles at pc034083.code3.com> writes:

>You'll *never* get 2X due to overhead (architectural as well as OS).
>Depending on how clean the hardware and OS is, the closer you'll get to 2X.
>I'm pretty impressed with Linux. It is probably 1.95 or better. (Just
>guessing from experience.) NT is worse, but probably 1.9 -- not 1.5!

Don't you EVER say *never*. MacOS still runs all the i/o and interrupt
handling off of the first CPU, so I get maybe 99.999% usage of additional
CPU's, but at most 97% of the cycles on the first one. Adding CPUs to a
MacOS machine causes client performance to super-scale at up to 2.1x the
single-cpu speed.

This is a special case because the cruncher's data fits entirely in
registers and its code fits entirely in the L1 cache, thus eliminating any
slowdowns due to bus contention.

But don't you EVER say *never*. :)

Andrew Meggs, content provider                  Antennahead Industries, Inc.
<mailto:insect at antennahead.com>                 <http://www.antennahead.com>

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