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Date: Sat, 10 May 1997 17:25:46 -0400
To: questions@freebsd.org
From: Michael Alwan <alwan@rma.edu>
Subject: advantages of symmetric processing
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To anyone interested:

I'm interested in a dual processor motherboard (i.e. Tyan Tomcat III Dual
[original Pentium]) and symmetric multiprocessing as a way of a) increasing
speed of apps under FreeBSD or WinNT b) taking advantage of falling Pentium
prices (original socket 7 Pentiums without MMX) c) using my present 120 MHZ
Pentium and d) allowing a relatively inexpensive upgrade path for a few
years to come.

On the other hand, there are other socket 7 processors like the AMD K6 with
all the 32 bit optimizations, faster clock speeds, and lower prices than
newer Intel stuff.  The upgrade path (beyond 266 MHZ) seems unpredictable,
and as far as I know, it can't be multiprocessed.

Here's my question.  All other things being equal (version of operating
system, system bus speed, amount of ram, kernel configuration, disk speed,
etc.)  which runs a given app faster--symmetric multiprocessing or faster
clock speeds with one processor?

Compare, say, two 120 MHZ Pentiums to one 200 MHZ Pentium Pro.  Do
something CPU-intensive in a database.  Which will come out ahead?  What is
the break-even point?  I'm less likely to be networking or using my machine
as a server and more likely to be image-processing or DTP or using a database.

I haven't been researching this for long, but everything I've read seems to
suggest adding a second processor doesn't increase the speed of a given
operation more than 50%.  There is a lot more information about the impact
of cpu clock speeds, obviously because most people have one cpu.  I also
realize that at the rate new hardware and software is coming out, any
prediction now might make no sense in 2 months.  I'm just looking for the
most bang for the bucks I have now.

If anyone has any answers experience, or opinions, I'd be really
interested.  It's hard to get a straight answer from a vendor.

Thanks,

Michael