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Thermal Characteristics and Power Consumption

Now that we have discussed in detail all the new power-saving technologies implemented by Intel in their new Pentium 4 6XX processors, it is high time we estimated their practical value in real-life applications.

For our testing experiments we assembled the following test system:

  • Mainboard: ASUS P5AD2-E Premium (LGA775, i925XE Express);
  • Memory: 1024MB DDR2-533 SDRAM (OCZ PC2 4300, 2 x 512MB, 4-4-4-11);
  • Graphics card: PowerColor RADEON X800 XT (PCI-E x16);
  • Storage subsystem: Maxtor MaXLine III 250GB (SATA150).

First of all, we measured the temperatures of LGA775 Pentium 4 6XX and Pentium 4 5XX processors. Among the latter CPUs we used the solutions based on Prescott E0 core stepping, i.e. the CPUs that support C1E and TM2. The frequencies of the tested CPUs were set to 2.8GHz, 3.0GHz, 3.2GHz, 3.4GHz and 3.6GHz, and those for the CPU on Prescott E0 core stepping – to 3.8GHz. The bus was working at its nominal frequency in all cases. The processor Vcore also stayed nominal. For all our tests we used the same boxed LGA775 cooler. The processor temperatures were measured with the help of a built-in on-die thermal diode. We measured all temperatures in two modes: in idle mode and under maximum workload created by a special S&M utility version 0.3.2, which is the best tool out there today for CPU heating experiments.

Besides the temperatures of the Pentium 4 5XX and 6XX processors, we also added the data for the Pentium 4 Extreme Edition 3.73GHz to the final diagrams. Although this CPU is also based on the same Prescott 2M core with N0 stepping, like all other Pentium 4 6XX processors, it doesn’t support C1E, TM2 and EIST technologies. That is why we are going to pay special attention to its thermal characteristics and power consumption.

As we see, Pentium 4 5XX and Pentium 4 6XX processors working at the same frequencies generate about the same amount of heat under maximum workload. It means that larger L2 cache memory hasn’t affected the thermal characteristics of the new CPUs at all. However, we would specifically like to draw your attention to the processors performance in idle mode. First of all, note that Pentium 4 5XX and Pentium 4 6XX run at the same temperatures independent of their nominal clock frequency in this mode. It can be explained by the fact that in idle mode these CPUs run in power-saving regime at 2.8GHz clock speed, independent of their nominal frequency. For example, Pentium 4 XE 3.73GHz , which doesn’t support C1E, TM2 and EIST technologies, heats up notably more in idle mode. It is actually quite logical, as it continues working at its nominal frequency in this mode unlike Pentium 4 5XX and 6XX processors.

Also, besides the temperature measurements, we also evaluated the power consumption of the Pentium 4 processors based on Prescott and Prescott 2M cores. For this purpose we took a special clump multimeter and measured the current in the 12V circuit powering the CPU. In other words, the data given below takes into account the performance index of the CPU power converter, that is why you may find these numbers a little bit higher than the actual processor power consumption values (about 10%):

The picture appears pretty much the same as the one we just saw for the temperatures. However, I have to point out that the new Prescott 2M based CPUs boast lower power consumption than the processors on the regular Prescott core even despite a larger number of transistors they use. This way there is quite a bit of reserve for further increase in the Pentium 4 6XX clock frequencies.

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