Improved Intel Turbo Boost status/control

Ivan Klymenko fidaj at
Mon Mar 12 19:33:20 UTC 2012

В Mon, 12 Mar 2012 21:15:35 +0200
Alexander Motin <mav at> пишет:

> Hi.
> I'd like to note that recent r232793 change to cpufreq(4) in HEAD
> opened simple access to the  Intel Turbo Boost status/control. I've
> found that at least two of my desktop systems (based Nehalem and
> SandyBridge Core i7s) with enabled Intel Turbo Boost in BIOS it is
> not use it by default, unless powerd is enabled. And before this
> change it was difficult to detect/fix.
> ACPI reports extra performance level with frequency 1MHz above the 
> nominal to control Intel Turbo Boost operation. It is not a bug, but 
> feature:
> dev.cpu.0.freq_levels: 2934/106000 2933/95000 2800/82000 ...
> In this case value 2933 means 2.93GHz, but 2934 means 3.2-3.6GHz.
> After boot with default settings I see:
> dev.cpu.0.freq: 2933
> , that means Turbo Boost is disabled.
> Enabling powerd or just adding to rc.conf
> performance_cpu_freq="HIGH"
> enables Turbo Boost and adds extra 10-20% to the system performance.
> Turbo Boost operation can be monitored in run-time via the PMC with 
> command that prints number or really executed cycles per CPU core:
> pmcstat -s unhalted-core-cycles -w 1

Thank you very much!
and as this option must be combined with state of the processor C1 C2

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