Processor use up after RAM upgrade

[eben]

Last night I upgraded my pfSense box.

It's still A PIII 550, but I removed the 3x128MB DIMMs and replaced them with 2 x 512MB DIMMs and 1 x 128MB DIMM.

Since the upgrade, my sustained processor use looks like it's come down, but I have lots of spikes.

Is this normal?
Should I remove the 128MB DIM and just the machine on a gig of RAM?

Any ideas or inputs would be most appreciated.