reliable/reproduceable benchmarks on SGI MIPS box

[Andrew Hume]

	I am running some benchmarks on a variety of machines
and in particular, on a SGI 4D/380, a multiprocesor with 8
33MHz R3000 cpus. my benchmark reads in about 1.1MB of text
into an internal buffer and then runs cpu bound for about
40s. total memory usage is <2MB; the machine's memory is 256MB.
The benchmarks are run with the machine in single user (Unix)
mode with normally mounted NFS filesystems unmounted. No other
processes (excpet paging daemon etc) are running.

	my problem is that I see quite large variations over
multiple runs of the same benchmark, sometimes as much as
1.26%. Now, the resolution of the timer is .01s and i should se
an accuracy of about .01/40 or .025%. I am a factor of 50 off this.
does anyone know how i can run these benchmarks so as to get reproducible
timings? (i note as an aside that just running the benchmarks on the cray
in multi-user mode yields variations of the order of .15% which is
satisfactory).

	andrew hume
	andrew at research.att.com