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tkalfaoglu 05-13-2006 12:49 AM

P4 and CPU Frequency scaling
Hi there. What should the kernel parms be for a hyperthreaded P4 to get
decent cpu speed throttling? (It's an ASUS P4800 P4 2.6, desktop).

My aim is to get frequency scaling work properly - that is, move from
a low CPU speed to full speed using the ondemand governor.

I tried enabling APM and ACPI (with all bells and whistles) in the kernel config, along with the CPU Frequency Scaling options. At startup I got an err in dmsg about APM not being SMP compliant, so I disabled that again at my next kernel build. (This is #26 SMP PREEMPT, downloading the most recent one just now :)

However, I only get a clock range from 2275000 hz to 2600000 hz.
I was hoping to go from something much lower to 2,6Ghz, auto-changing depending on the load.

Any ideas what I should tweak?

Attached: relevant-looking things.

[root@tk cpufreq]# more cpuinfo_min_freq
[root@tk cpufreq]# more cpuinfo_max_freq
[root@tk cpufreq]# more scaling_available_frequencies
2275000 2600000
[root@tk cpufreq]# more scaling_available_governors
conservative ondemand powersave userspace performance
[root@tk cpufreq]# more scaling_governor
[root@tk cpufreq]#

│[*] CPU Frequency scaling │ │
│ │[*] Enable CPUfreq debugging │ │
│ │ <*> CPU frequency translation statistics │ │
│ │[*] CPU frequency translation statistics details │ │
│ │ Default CPUFreq governor (userspace) ---> │ │
│ │ <*> 'performance' governor │ │
│ │ <*> 'powersave' governor │ │
│ │ --- 'userspace' governor for userspace frequency scaling │ │
│ │ <*> 'ondemand' cpufreq policy governor │ │
│ │ <*> 'conservative' cpufreq governor │ │
│ │ --- CPUFreq processor drivers │ │
│ │ <*> ACPI Processor P-States driver │ │
│ │ < > AMD Mobile K6-2/K6-3 PowerNow! │ │
│ │ < > AMD Mobile Athlon/Duron PowerNow! │ │
│ │ < > AMD Opteron/Athlon64 PowerNow! │ │
│ │ < > Cyrix MediaGX/NatSemi Geode Suspend Modulation │ │
│ │ <*> Intel Enhanced SpeedStep │ │
│ │[*] Use ACPI tables to decode valid frequency/voltage pairs │ │
│ │[*] Built-in tables for Banias CPUs │ │
│ │ <*> Intel Speedstep on ICH-M chipsets (ioport interface) │ │
│ │ <*> Intel SpeedStep on 440BX/ZX/MX chipsets (SMI interface) │ │
│ │ <*> Intel Pentium 4 clock modulation │ │
│ │ < > nVidia nForce2 FSB changing

Thanks a lot,
Turgut Kalfaoglu

guzzi 05-13-2006 07:49 PM

speed reduction
Hello tkalfaoglu

Why speed throttling on a desktop?

I am not wanting to split hairs, or be a pain, but I have never though about doing this, and am curious about what you think. You may be on to something I could use also.

I have a Sony laptop with a desktop P4 (not a mobile processor) 2.4GHz CPU, that can go from 300 MHz to 2.4 in 8 steps. The most intensive thing ever done on this unit is compiling a kernel. In that process, the fan will spin faster as the CPU tries to get hotter, but it has never gotten so warm that the CPU speed is reduced.

The only time CPU speed reduction has been used, has been when running on the battery. On battery, I get less than 2 hours operation at 2.4GHz, and I have no idea how long it lasts at 300MHz. At Internet Cafe's I manually select 300Mhz, and it runs long enough for me to surf, do my work related activities, drink several cups of coffey and eat at least one pastry.

But, why would you want a desktop unit to run less than full speed?

tkalfaoglu 05-14-2006 12:40 AM

Hi there. this is a machine that stays on permanantly.
Therefore I would like to extend its life, reduce the power consuption and reduce its heat output.

Thanks for the feedback,

Hunter2 05-31-2006 10:56 AM


I've got a P4 (no HT) on my Toshiba laptop, not sure if it's a mobile version or not.
When I config the kernel with ACPI P-States *AND* P4-clockmod drivers, I get a warning that I should use ACPI P-states or the ICH-M driver instead, and I only get 2 possible frequences: 2.4ghz and 3.06 ghz, in one big step. When I disable p4-clockmod and just use ACPI P-States, I get either 1.60ghz OR 3.06ghz, in one even bigger step.

In each case I tested, and both cpu speeds worked, so I know my CPU can run at steps 1.6ghz, 2.4ghz, and 3.06ghz at least (and probably a lot more), but for some reason I can only get 2 frequency steps at a time - looks like tkalfaoglu has a similar problem too. Also, the ICH-M driver just doesn't work at all (cpufreq says there's no drivers for my CPU), even though the warning said it detected a CPU of that type. Do you know what drivers I need to get scaling to work properly? (and guzzi, can you post your config for ACPI/APM/cpufreq?)

It's particularly important to me, because my laptop is running *really* hot, i.e. the keyboard is uncomfortably warm even when the system has been idle for hours, and I'm also getting pretty bad battery life.


As an aside, do the drivers work simultaneously, or is it a one-or-the-other arrangement, i.e. if multiple drivers are compatible I need to pick the *right* one?

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