How to use Core i7 turbo

[Josh Carroll]

I'm running FreeBSD 8.2-RELEASE/amd64 on a Core i7 2600k system with
the ASUS P8Z68-V PRO motherboard.

I'm trying to get the turbo mode
(http://en.wikipedia.org/wiki/Intel_Turbo_Boost) to work in FreeBSD,
but I can't seem to make it happen. I've tried:

1. auto settings (3.4 GHz base frequency, 3.8 GHz turbo (on one core)
or 3.5 GHz on all cores).

2. manually setting the turbo ratio per core to 38 or 40

3. setting the turbo ratio to 40 "for all cores"

I'm running an ffmpeg encode to test the performance, and I'm seeing
identical results for both a single-threaded encode (e.g. ffmpeg
without -threads) and also if I specify 4, 8 or auto (0) threads with
ffmpeg. No matter what I do, the encode runs in the same amount of
time.

hw.clockrate reports 3400, and dev.cpu.0.freq reports 2900 sometimes
and 3401 other times, but never over 3400.

I tried setting cx_lowest to C3 for all cores and then running a
single threaded ffmpeg encode, in the hopes it was just the other 3
cores idling so that ffmpeg could run on the single core. But that
made things much slower (2x slower in fact) for a mult-threaded ffmpeg
encode, and about the same for a single threaded ffmpeg encode.

Do I need to be running powerd or setting some other sysctl or loader
tunables to be able to use this turbo feature? Ideally, I'd like to
set things up so they run at 3.8 or 4.0 at all times, but I don't know
if there is a way with these SandyBridge CPUs to just do a "simple
overclock" as was possible in the past. I don't plan to run it at 4
GHz forever, I just figured I should be able to see at least a 10-15%
increase in speed (if not more) if the turbo were working. And so far
I'm not seeing any evidence of the turbo working.

I appreciate any help you all can provide.

Regards,
Josh