Updated: Tuning Cool'n'Quiet: Maximize Power And Performance

Test Results: Idle

Both minimum and minimum average numbers are taken and calculated from measurement results five minutes after booting. The system is idle at this time, though some spikes of activity still occur.

Athlon X2 7750

The results are very interesting indeed. As noted before, running Cool'n'Quiet with the Windows power policy set to “Balanced” offered minimal savings. It’s only when we change the voltage that we're able to significantly save more power--about 13 watts lower consumption, or a total of 20 watts compared to running without power management. That's a savings of 25%.

Athlon X2 7850

The Athlon X2 7850 exhibits a different behavior, more likely since it correctly applies a lower voltage when Cool'n'Quiet is enabled. Enabling Cool'n'Quiet saved around 13 watts, and lowering the operating voltage for both the processor’s p-states saves us an additional 9 watts (total savings are 22 watts, or 22%).

Athlon II X2 250

The Athlon II X2 250 is probably the least power-hungry processor in AMD’s entire lineup; it's certainly the least power-hungry of the CPUs we've tested here. With Cool'n'Quiet enabled, system power consumption with this processor is much lower than the Athlon X2 7750 or 7850. With tweaked voltages, you can see even lower levels of consumption. We went from around 76 watts with no power management to 72 watts with Cool'n'Quiet. We even saw 63 watts when we tweaked the p-state voltages.

Note: on the new Socket AM3 platform, we were able to go well below the numbers above. Idle power consumption drops to 39-41 watts when undervolted. That's quite a jump, even when compared on the TA790GX 128M, which sits at 50 watts idle.

  • DrgnRebrn
    Nice article! I'm curious to know if the "e" CPUs can be affected in the same way, such as the Phenom II X3 705e. I have chosen this CPU for a HTPC build because of it's already low 65W TDP. Also, what are the effect to power usage when using ACC features & enabling dormant cores?
  • cyberkuberiah
    On the behalf of all readers , Welcome , and so to say , Hi! , Arnawa Widagda :)
  • Inf3rnal
    I'd like to see same article about Intel i5/i7 power setting tweaking.
  • razor512
    did any of these changes negatively effect performance?
  • Very good article! Undervolting it's a great tweak to make and most of the people don't even know that it is possible as well as overvolting, getting a power efficient processor for no money! Thanks tom's for caring about this matter.
  • nukemaster
    My old A64 3200+ is about to get this treatment
  • autoimmune
    Inf3rnalI'd like to see same article about Intel i5/i7 power setting tweaking. O my GOD i bet the writers at Toms Hardware had not thought of that, and are not currently in the process of writing that article!
  • whiz
  • i love you guys. i have just the system that i am using as HTPC. i was wondering about ways to reduce the power usage as i dont use it for hardcore gaming or any other cpu intensive jobs. all i use it for watching blurays and tv and other movies and songs. i have an ASROCK 790gxh 128M mobo. and 1thlon x2 7750 kuma, that i bought from newegg for $59 (darn steal for the performance it gives. the machine has almost zero latency for any operation)
  • Jerky_san
    Anyone know where to get k10stat?