cpu MHz

[i92guboj]

It's not noticeable. Note that this feature is supported at hardware level, so it's really fast. You can save a few bucks on the bill of your electric supplier.

[bigtomrodney]

I don't know. I probably don't need to. The reason I was looking to speed it up was I assumed it was running at that speed all the time.

How quickly will it increase to its full value if processesing power is needed?

Speed scaling is great nowadays. It used to be awful in the P4/Athlon era but it's really worth using now. With my Intel Q6600 it clocks up immediately on demand. The thing to bear in mind is that because you have four cores your threads will be spread out across them and thus you will not need to run them at full speed as much as a single core CPU.

There is a cool applet you can get for the Gnome panel that shows you your CPU frequency. I have four of them setup, one per core and can watch the cores jump up and down as needed. Pretty cool for sure, but it did show me how little I actually need the full speed, making me feel better about leaving the PC on at lower power

[EndianX]

Thanks for all the info.

The only cpu scaling I've had experience with to date is when my dell laptop would constantly overheat and the cpu would compensate by reverting to bronze-age technology. So my initial reaction was to put a stop to it.

So that 1.3Ghz is my min frequency it seems. Because, as i92guboj said, this is implemented at a hardware level, is that going to be the only option my processor supports other than full speed? Or is that some sort of kernel limitation?

/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies

2600000 1300000

[bigtomrodney]

I think you can force other frequencies to run but I've found that these modern CPUs are great for managing themselves and can really be left to their own devices.

My own CPU appears to run at either 1.6GHz or 2.4GHz, but I recently found out it makes a stopover at 2.0GHz too. I think it's more a case that if there is a heavy workload, just throw everything at it.

[i92guboj]

This tool could provide you some info:

$ cpufreq-info
cpufrequtils 005: cpufreq-info (C) Dominik Brodowski 2004-2006
Report errors and bugs to cpufreq@vger.kernel.org, please.
analyzing CPU 0:
  driver: powernow-k8
  CPUs which need to switch frequency at the same time: 0
  hardware limits: 1000 MHz - 1.80 GHz
  available frequency steps: 1.80 GHz, 1000 MHz
  available cpufreq governors: conservative, ondemand, powersave, userspace, performance
  current policy: frequency should be within 1000 MHz and 1.80 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.80 GHz.
  cpufreq stats: 1.80 GHz:21,82%, 1000 MHz:78,18%  (202)

However I don't know if there's a way to add more steps or this depends entirely on the hardware. I never felt the need to look on this, it just works ok

[blinky]

I think the limits are hardware imposed, what it's possibly doing is dynamically changing the CPU multiplier.

More general at CPU frequency scaling in Linux with cpufreq

[mrj10e12]

How quickly will it increase to its full value if processesing power is needed?

I was thinking to myself, without considering the CPU scaling and controls of a on-board fan and cooling system, which is designed most of the time by the board manufacturer, the correct answer would be...

"Faster than you can throw things at it, unless you write pure ASM code in your apps."