Freezing with FreeBSD

[retisas]

I installed FreeBSD 4.7 (I know, it's old version, but the problem is the same in newer 4.* versions).
Everything worked well except for the fallowing shell "program" (in zsh):
while true; do; done
(don't ask why i tried it )
It "worked" well and my cpumeter showed 50% usage. Then I run this difficult program in an other terminal, and 5-10 seconds later the system freezed. (I had tu reset the computer)

OK, there is a bug in FreeBSD 4.* - I thought - , let's try version 5.* :
Heureka The system doesn't freeze if I run this program twice (or more) in one time.
It's good, but the system isn't stable. (FreeBSD 5.2.1) It freeses randomly (about once a week...), and I don't know what the reason is.
Any idea?

I'm using nj BIOS. (Should I update it?)

[BCN]

check the caps