Is it possible to put the Firefox cache directory somewhere else than the USB?

My environment: Windows-XP in a public library. PAC on a USB stick.
I previously installed Firefox Developer Edition and tried to run with it. It appeared to totally overwhelm the computer.
Nothing moved! I wound up frequently terminating my session to clean everything up, then logging in again.

I don't expect much running off a stick, but a preliminary analysis suggests the likely culprit here is the cache structure.
If there is a setting that allows moving the cache into the %TEMP% ($TMP) directory, I expect the program would pick up
lots of speed.
If that requires getting into the upstream source, well I had a decent name in the Mozilla community when I was younger and
sharper. But really, the hit is so much worse because of the slowness of the USB, so it possibly only affects PAC.