Optimizing Your Phenom II Overclock For Efficiency

Conclusion

AMD’s Black Edition (BE) processors make it really easy to overclock your processor, as these CPUs can be configured to any clock speed setting you like--only the processors’ physical limits will stop you. In contrast, regular edition CPUs will support only those processor multiplier settings that are required to operate at the rated speed or lower, in many cases (which opens the door to some interesting comparisons between multiplier versus bus speed overclocking, too).

Overclocking regular processors thus means altering the base clock in order to receive a higher core clock speed, which may require faster memory or better cooling. From this point of view, AMD’s Phenom II X4 940 Black Edition offers an excellent value for enthusiasts, giving them high performance and maximum (over) clocking flexibility at reasonable prices.

Performance And Efficiency Scale Nicely With Phenom II

The performance results were pretty straightforward. each clock speed bump translates into measurably increased performance in almost all benchmarks and applications we used. Since we did not have to increase the processor voltage at up to 3.4 GHz, the resulting efficiency kept increasing. Better performance at marginally increased power consumption means better power efficiency. Even the 3.6 GHz setting, which required a manual voltage setting slightly above the default value, resulted in excellent power efficiency.

Refrain From Voltage Increase

The only clock speed setting we recommend against using was the 3.8 GHz configuration, which required the core voltage to be increased more than the resulting clock speed was able to yield in performance. We also had an issue where Cool’n’Quiet would not kick in any more, despite being enabled in the BIOS. This resulted in exorbitant idle power consumption of +43 W when compared to default speed and also +47% increased peak power. Since the resulting performance does not increase by this much, the resulting power efficiency shows a considerable drop.

Clearly, the current architecture at the current stepping and voltage performs best in between 3.2 and 3.4 GHz. 3.6 GHz provided even better power efficiency and increased performance, but we had to manually adjust the processor voltage. Knowing this, we’d be eager to see even faster versions of AMD’s Phenom II processors, as the current clock speeds do not unfold the power efficiency that is hidden in AMD’s current architecture.

Editor's Note: In discussing the 3.8 GHz Cool'n'Quiet issue with representatives at AMD, we touched on a concept that we'd previously never really talked about on Tom's Hardware: its Fusion gaming utility.

Fusion might be a good way for enthusiasts to better control power consumption, as it allows the system to run at its stock clock speed--with Cool'n'Quiet enabled during periods of low utilitzation. Before you fire up a game, a simple button-press instantiates a configured profile, setting whichever frequencies and voltages you've specified in the Overdrive utility, garning that extra performance. By switching back and forth in this manner, you can enable the benefit of overclocking almost on-demand, without the inconvenience of setting each parameter manually.