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Date: Fri, 11 Sep 2009 11:23:11 +1000
From: Andrew Snow <andrew@modulus.org>
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To: Pierre-Luc Drouin <pldrouin@pldrouin.net>, 
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Subject: Re: How to enable CPU turbo mode on FreeBSD?
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Pierre-Luc Drouin wrote:

> I have an overclocked i7 920 CPU for which I have enabled Turbo Mode in 
> the BIOS (21x multiplier). The base clock is set at 190 MHz, so the CPU 
> frequency with Turbo mode activated should be 3990 MHz. However the 
> maximum value FreeBSD amd64 shows for the CPU frequency in dmesg and 
> sysctl is 3790 MHz. How can I enable the Turbo Mode?

The turbo mode doesn't show up in dmesg or sysctl, it dynamically 
overclocks inside the CPU.  Also, some motherboards silently disable 
turbo mode when you overclock the base clock.

You may need to use a benchmark running on 1 vs 4 cores to see if turbo 
mode is having any effect.

- Andrew