There is a marvelous book I recommend:

	In Search of Clusters, 2nd Ed.
	Gregory Pfister

It discusses multiprocessor configurations extensively, in an
accessible manner.

In an MP configuration (kernel runs on only one processor), you
will bottleneck on the processor running the kernel. How soon that
happens depends on what type of job mix (computing load) you have.
If you're I/O intensive, MP may be a net-lose, because switching
processors has some cost in L1/L2 cache coherency and such. If you're
*totally* CPU-bound (e.g. cracking RC5-64 keys, SETI@Home, GIMPS),
then MP should win quite nicely.

The trick is getting your job mix to spend more than 50% of its
time in user mode, computing, instead of making system calls. The
more processors you have, the more CPU-bound jobs you need to take
full advantage of the system.

There is a short paper about the very first MP UNIX configuration
(a two-headed VAX-11/780) available at

	http://ghg.ecn.purdue.edu/vax/paper.html

George Goble also lights his BBQ grill with LOX to make sure that
it takes minimum time to be ready to grill those hot dogs and
hamburgers. See

	http://ghg.ecn.purdue.edu/

It's quite a sight.

	Erik E. Fair	fair@clock.org