John Baldwin wrote:
On Thursday 10 September 2009 8:57:32 pm Pierre-Luc Drouin wrote:
Hi,
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?
CPU: Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz (3790.52-MHz
K8-class CPU)
machdep.acpi_timer_freq: 3579545
machdep.tsc_freq: 3790522507
machdep.i8254_freq: 1193182
dev.cpu.0.freq: 349
dev.cpu.0.freq_levels: 2793/130000 2443/113750 2094/97500 1745/81250
1396/65000 1047/48750 698/32500 349/16250
You have to enable C2/C3 sleep states (possibly in your BIOS). However,
FreeBD doesn't currently handle this but so well since that will probably
turn off the local APIC timer interrupt when the CPU is idle causing FreeBSD
to miss clock interrupts.
Sorry I am not sure exactly what you are referring to. Do you mean that
I need to enable C2/C3 states in order to have the correct max CPU freq
value displayed at boot time/in sysctl, or you mean that I need these
states in order to be able to use the Turbo Mode at all? Right now in
the BIOS I had the following features disabled to test the overclocking
(I was following what is recommended to do for Windows users to run
stress tests):
-Intel SpeedStep: Use this function to enable the Intel SpeedStep
technology (EIST)
-CxE Function: This function allows you to select the lowest C state
supported according as CPU and MB. The options are Auto, Disabled, C1,
C1E, C3 and C6
Thanks!
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