Date: Fri, 11 Sep 2009 11:46:13 -0400 From: Pierre-Luc Drouin <pldrouin@pldrouin.net> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-stable@freebsd.org Subject: Re: How to enable CPU turbo mode on FreeBSD? Message-ID: <4AAA70C5.5090408@pldrouin.net> In-Reply-To: <200909111105.01619.jhb@freebsd.org> References: <4AA9A07C.4050200@pldrouin.net> <200909111105.01619.jhb@freebsd.org>
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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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