specifying RAM size at boot?

[Daniel Ellard]

I am experimenting with the relationship between RAM size and various
file system performance characteristics.  I've got a machine with a
large amount of RAM; what I want is to be able to tell FreeBSD to only
use a fraction of it, so I can pretend the machine has various
different amounts of RAM.  The goal is to run my tests and have them
run just as if the machine actually had that much RAM.  Anyone know
how to do this?

I thought this was configurable by setting a variable in
/boot/loader.conf and rebooting, but I haven't been able to find the
right variable(s).  (someone suggested MAXMEM, but this doesn'
seem to do anything at all.)

I'm using FreeBSD 4.8.

Thanks,
	-Dan