CPUFreq

Wed Nov 30 20:43:07 UTC 2011

Hello
I think you don't even need to go 'back' to boot frequency. I suggest using 
powerd(8) to save some power and lower the temperature.
Put it in /etc/rc.conf :
powerd_enable="YES"
powerd_flags="-a adp -m 800"

Ofc flags can be tuned to your needs. Powerd will be watching your system load 
and change freq dynamically depends on how heavy it is.

Little off-topic:
In my case i use Intel Core i5 2500k overclocked from 3.3k to 4.2k in bios, 
but in FreeBSD
dev.cpu.0.freq = 4101
dev.cpu.0.freq_levels: 4101/300000 4000/300000 3900/300000 3800/300000 
3700/300000 3600/300000 3500/300000 3400/300000 3300/300000 3200/300000 
3100/300000 3000/300000 2900/300000 2800/300000 2700/300000 2600/300000 
2500/300000 2187/262500 1875/225000 1600/91000 1400/79625 1200/68250 
1000/56875 800/45500 600/34125 400/22750 200/11375

not something around 4200... i can live with it, but only wondering why its 
lower than bios settings ?