# cpu frequency scaling with overclocking

## highland

hello

i have core duo e6600 overclocked to 3Ghz.

Does anybody used cpu frequency scaling with overclocked CPU ?

When i overclock cpu in bios i receive:

arrakis cpu0 # cpufreq-info

cpufrequtils 002: cpufreq-info (C) Dominik Brodowski 2004-2006

Report errors and bugs to linux@brodo.de, please.

analyzing CPU 0:

  no or unknown cpufreq driver is active on this CPU

analyzing CPU 1:

  no or unknown cpufreq driver is active on this CPU

When i disable overclocking cpufreq works fine but only to nominal (2.4Ghz) frequency (can not overclock).

Has anybody used custom governor with overclocked CPU ?

Thanx

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## darklegion

Your motherboard's bios is probably disabling cpufreq when overclocking is being used; some consider this a stability feature.I know my Gigabyte ep46-ds3 won't let met use cpufreq but my older Abit ip35e did.If your overclock is rock stable and you're not pushing the voltage outside intel's specs, I wouldn't worry about it too much.You won't waste much extra power either, as most of the power is being consumed while it's actually doing something; when it's idle the savings are negligible.

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## highland

I have gigabyte P965DS3. Bios updated. When overclocked to 3.4Ghz it has seriously increased voltage.

When system is idle does the CPU decrease voltage, frequency or what (to minimize power consumption) ?

(does it become automatically in linux or i have to launch some acpi daemons or what ?)

Can i check it from system somehow ?

Thanx

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## bbgermany

When you overclock you CPU with a raised VCore, all SpeedStep option will be disabled by the BIOS by default. So you wont have the access to the frequency scaling anymore. If you overclock at default VCore, you should be able to use the frequency scaling again (but this isnt default on any board). 

I should mention, that if you overclock without VCore raising, the clock speed of your CPU will fall down to default speed (e6600 2.4GHz) at full speed. So it doesnt make sense anymore to overclock it.

bb

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## PinguinoLoco

I hava an e6600 at 3GHz on a Gigabyte 965PDS4 with stock voltage. CPU frequency sacaling works perfectly (ondemand and performance governors). The two states at which the processor can run are 2 GHz and 3 GHz (1.6 GHz and 2.4 GHz without overclocking). VCores are also adjusted depending on the speed. The only issue is that the speeds are shown by cpufreq-info as if there was no overclocking, but it is active (dmidecode shows the real speed and the performance bump is there).

I had to activate two options in the BIOS: EIST and C1E. Be sure to test the system stability thoroughly.

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## Monkeh

 *bbgermany wrote:*   

> If you overclock at default VCore, you should be able to use the frequency scaling again (but this isnt default on any board). 
> 
> I should mention, that if you overclock without VCore raising, the clock speed of your CPU will fall down to default speed (e6600 2.4GHz) at full speed. So it doesnt make sense anymore to overclock it.

 

My IP35 Pro disagrees.

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## bbgermany

This could be, coz Abit always made a difference when overclocking. My P5WDH even disables SpeedStep with my current CPU without raising the VCore. But this could be a limitation of the chipset as well.

bb

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## drescherjm

 *Quote:*   

> dmidecode shows the real speed and the performance bump is there

 

That is interesting I gave up when /proc/cpuinfo only showed base clock

```
processor       : 1

vendor_id       : GenuineIntel

cpu family      : 6

model           : 23

model name      : Intel(R) Core(TM)2 Quad  CPU   Q9550  @ 2.83GHz

stepping        : 7

cpu MHz         : 2833.000

cache size      : 6144 KB

physical id     : 0

siblings        : 4

core id         : 1

cpu cores       : 4

apicid          : 1

initial apicid  : 1

fpu             : yes

fpu_exception   : yes

cpuid level     : 10

wp              : yes

flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr sse4_1 lahf_lm

bogomips        : 5798.67

clflush size    : 64

cache_alignment : 64

address sizes   : 36 bits physical, 48 bits virtual

power management:

```

```
Handle 0x0004, DMI type 4, 40 bytes

Processor Information

        Socket Designation: LGA 775

        Type: Central Processor

        Family: <OUT OF SPEC>

        Manufacturer: Intel

        ID: 77 06 01 00 FF FB EB BF

        Version: Intel(R) Core(TM)2 Quad CPU Q9550 @ 2.83GHz

        Voltage: 1.2 V

        External Clock: 343 MHz

        Max Speed: 3800 MHz

        Current Speed: 2916 MHz

        Status: Populated, Enabled

        Upgrade: Other

        L1 Cache Handle: 0x0005

        L2 Cache Handle: 0x0006

        L3 Cache Handle: 0x0007

        Serial Number: To Be Filled By O.E.M.

        Asset Tag: To Be Filled By O.E.M.

        Part Number: To Be Filled By O.E.M.

        Core Count: 4

        Core Enabled: 4

        Thread Count: 4

        Characteristics:

                64-bit capable

```

I guess its time to do a real overclock to see if there actually is a performance increase. Going from 2.83 GHz to 2.916 is too small of a bump to see.

If this does not work I was thinking of tinkering with the cpufreq driver like the folks at linux-phc did to undervolt cpus:

http://www.linux-phc.org/index.php?sid=ba0356aade078116cf7d4c04a0bc53e5

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## drescherjm

I got this to work with a 3 line change in my kernel source. I am testing the effects of this and will post the details if the testing goes successful.

BTW, I did not see any performance increase over the base frequency with speedstep and without the kernel change.

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## devsk

cpufreq has weird interaction with OC. On i7 920, what I noticed is that cpufreq-info displays clocks based on the default BCLK of 133 for 20x multi (like max of 19x133=2.533Ghz) although the system runs fine with both performance and ondemand governors with highest clock (equaling the OC, which is 19x221=4.2Ghz).

But the thing does work with OC. I am using latest kernel, so your mileage may vary.

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## drescherjm

While I was playing with this I noticed that my core2 quad q9550 does not use any more power while at idle at 2.97GHz then it does at 2.1GHz so I may drop this. I verified this at work on a barebones Q9650.

The system (ASUS P5Q), nvidia 7200GS, Q9650 and 4GB of corsair DDR2 memory netted

58W total system power at idle as measured by a killawatt meter

After setting cpufreq and advanced C states in the bios this was

reduced the wall power to 46W with or without the acpi-cpufreq driver

loaded.

This is completely different in my observations with AMD processors. I mean with AMD K8 chips reducing the frequency at idle makes a 20W or so difference.

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