Overclocking

Before reporting on our practical overclocking experiments with a Pentium M, we want to say that even though we tested the senior model of the series, you should not think that the overclocking potential of this CPU is poor. The Pentium M is just targeted at the mobile sector of the market, and such products must comply with the strict heat dissipation requirements. That is, the frequency growth of the Pentium M series is limited by the maximum typical heat dissipation rather than by the architecture or the current tech process. In other words, the frequency bar of Pentium M processors may go much higher than the frequencies of the current top models of this series.

So, it’s the more interesting to find the frequency limit of the Pentium M. To do this experimentally, we assembled a computer with an ASUS P4C800-E Deluxe mainboard and an ASUS CT-479 adapter. Then, using the cooler enclosed with the adapter, we overclocked our sample of the Pentium M 780. We should note that the ASUS CT-479 somewhat limits the mainboard’s overclocking options. Particularly, the option of adjusting the multiplier coefficient vanishes from the BIOS Setup (this multiplier can normally be reduced below the default value for Pentium M processors that support Enhanced Intel SpeedStep). Moreover, some mainboards with an ASUS CT-479 installed refuse to change the CPU voltage. The ASUS P4C800-E Deluxe, however, was free from the latter disadvantage. The default frequency of the Pentium M 780 is 2.26GHz, and we first of all wanted to know the highest frequency of this processor without increasing the voltage of the core. The default FSB frequency of this processor is 133MHz; the CPU’s default multiplier is 17x.

The Pentium M 780 did permit to increase its operational frequency considerably. Steadily lifting the FSB frequency up, we found the limit at 160MHz. The FSB frequency being 160MHz, the processor worked at 2.72GHz. In other words, the default CPU frequency grew up by 20% at overclocking!

So, the senior model in the Pentium M series has a 20% reserve of frequency. It is natural with a mobile CPU, but it would be a sensation if a senior desktop processor were to show such a good overclockability.

Recalling that Pentium III processors used to overclock better at higher voltages, we decided to give more voltage to our Pentium M, too. Having increased Vcore by 0.1V above the default, we got some better results at overclocking: 166MHz was the maximum FSB frequency at which the processor was stable. That is, the highest stable frequency of the processor with 1.48V Vcore was 2.82GHz. This is 25% above the default frequency of this model!

So, it’s a rewarding business to overclock a Pentium M. Even senior models of this series are capable of working at frequencies high above their default ones.

Obviously, junior models of this family can please you even more at overclocking. A very nice thing about the ASUS CT-479 adapter is that it permits to overclock a Pentium M using almost all of the mainboard’s options. The adapter being absolutely transparent to the CPU and mainboard, you overclock your Pentium M just as you would a regular Socket 478 processor. Of course, the increased voltage and frequency of the processor result in higher heat dissipation and power consumption. For example, the Pentium M consumes as much as 40.8 watts under load if it is clocked at 2.82MHz. This does not fit into the standard thermal design power of this processor.

We can suppose that the overclocking results will be much better if the cooling system is more efficient, but unfortunately you can’t use standard Socket 478 coolers with the Pentium M if you use an ASUS CT-479 converter. So if you’re into serious overclocking, the main problem you’ll be facing is creating a unique and efficient cooling system.