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Subject: MP system info

Author: K. Burcham

Date: 06:06:36 05/28/02






In absolute terms, the 8-way Pentium 3 Xeon systems are only 44% faster than the
4-way ones, which means that with the 4 extra CPUs, the system only gets 1.76
CPUs worth of extra performance, which is poor value for money. This level of
scalability is not that surprising since each group of 4 CPUs share 0.8GByte/s
of memory bandwidth. As a side note, it seems likely though that 252.eon fits
almost perfectly into the 2MByte cache the Pentium 3 Xeons have as it gets
nearly linear scalability - the higher the cache hit rate, the less main memory
is needed, which leaves more for the other CPUs.

Even worse, in some tests, the 8-way system actually does worse than the 4-way
system, and this could possibly be due to differences in the chipsets or because
the extra contention itself on the shared Pentium system bus causes efficiency
to drop. It's unlikely that the compilers/OS would have made much difference as
for each CPU type the tests were done at similar times with the same compilers.


http://www.aceshardware.com/read.jsp?id=45000338

kburcham




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