I've seen a number of posts on how to get the unfortunate default power-saver
state from 667mhz to 800mhz, in fact I was one of those posts on the OpenBSD
list today.  I spent half a day hacking openfirmware and was met with success.
The following will do the trick.

Boot into Openfirmware

Type EXACTLY THE FOLLOWING (with spaces)

nvedit<return>
" /cpus/PowerPC,G4@0" select-dev<return>
2faf0800 " clock-frequency" get-my-property 2drop !<return>
00000000 " force-reduced-speed" get-my-property 2drop !<return>

(Type Ctrl-C to exit editor)

nvstore<return>
setenv use-nvramrc? true<return>
reset-all

(Laptop will reboot, then enter normal boot hd command to boot {Open,Net}BSD)

dmesg will now report 800mhz! :)

-- 
Mark Grimes <mark@openbsd.org>
The OpenBSD Project