[Soekris] Idle temperature under various operating systems

[RB]

I've noticed something with my 4501s (and with other x86 hardware, for
that matter), that I find a matter of curiosity.

When running FreeBSD (m0n0wall or it's derivative pfSense), my
machines are palpably warm, even when completely idle.  I've not taken
any temperature readings, but one can hold their hand over the naked
board and feel heat radiating off, and the metal cases they're in are
warm to the touch.

However, under Linux (OpenWRT, GNAP) when the machines are idle,
they're completely cool - can't feel [much] warmth, and the cases are
always cool to the touch.  If I run a CPU soaker, then they warm up to
temperatures similar to what the ones running FreeBSD reach at idle.
Does the FBSD kernel have a busy-wait, or does it not do no-ops,
or...?  Without doing any scientific testing, I can say that they're
both responsive and seem to perform similarly under the moderate (home
router) loads I put on them.

Any insight?


RB