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Power Consumption and Heat Dissipation

Since the new 45nm manufacturing technology should definitely affect the electrical and thermal characteristics of the new processors, we decided to pay special attention to practical investigation of these parameters in the new CPUs.

First of all, we measured the operational temperature of our testing participants in idle mode and under high workload. During the tests we used the same Zalman CNPS9700 LED cooler for all CPUs. Enhanced Intel SpeedStep and Cool’n’Quiet 2.0 power-saving technologies were activated. By the way, Wolfdale processors, just like their predecessors, drop the frequency multiplier to 6x in case the workload is low.

CPUs were loaded using Prime95 25.5 utility. The temperature readings were taken with CoreTemp 0.96 utility. The obtained results are given in the table below:

As we have expected, CPUs on 45nm core are overall cooler than their predecessors on Core micro-architecture. However, the temperature different under 100% workload makes only 4-5 degrees. The thing is that Wolfdale processor core is smaller and features higher transistor density within a semiconductor die, which makes it a little harder for the heat flow to dissipate properly. That is why Wolfdale and Conroe heat up almost identically in idle mode. As for the relatively low temperature of AMD Athlon 64 X2 6400+, with twice as high TDP as that of Core 2 Duo actually, it can be explained by the not very best location of the on-die thermal sensor that is situated quite far from the hottest spots of the processor’s semiconductor die.

Everything we have just said indicates that CPU temperature measurements still offer pretty subjective judgment. Therefore, we decided to pay due attention to power consumption tests, too, that should fully reveal the advantages of the new 45nm core. During our experiments we measured the current going though the processor voltage regulator circuitry. This way we could estimate the actual CPU power consumption disregarding the losses in the voltage regulator circuitry.

The new processors manufactured with 45nm process performed more than impressively. In fact, we didn’t expect the results to be any different, as the new production technology allowed reducing the leakage current thanks to the innovative transistors with metal gate and high-k dielectric. As a result, the power consumption of the new Wolfdale processor under workload is equal to that of two 2-3 year-old processors in idle mode. Actually, Athlon 64 X2 results stress this dramatic difference between the processor generations even more, as its micro-architecture hasn’t been optimized for high performance-per-watt standards.

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