Heat Dissipation and Power Consumption

In fact, the transition of the Athlon 64 processor family to the new 90nm Winchester core doesn’t lead to any features changes or working frequency increase for this CPU family. However, it would be incorrect to believe that the ordinary users, who are not that much into overclocking, cannot benefit from that at all. The thing is that the new AMD processors on Winchester core feature lower power consumption and hence lower heat dissipation, which are pretty noticeable and important parameters I should say. According to the official specifications revealed by AMD, the CPUs on Winchester core generate maximum 67W of heat, which is 25% lower than the top heat dissipation of Athlon 64 processors on 130nm cores. However, what is its actual practical value? In order to answer this question we tested the new Athlon 64 CPU and compared its thermal parameters with those of the similar Athlon 64 processors but based on the older NewCastle core.

The testing was carried out on the same platform as in the previous case (during overclocking experiments). During the tests we compared the temperature of Socket 939 Athlon 64 processors on Winchester core and Athlon 64 processors on NewCastle core working at the frequencies from 1.8GHz to 2.4GHz. Note that we set the 1.8GHz, 2.0GHz and 2.2GHz frequencies with the corresponding frequency multiplier, i.e. as 9x200MHz, 10x200MHz and 11x200MHz respectively, while the 2.4GHz core clock was achieved as a result of CPU overclocking by raising the FSB frequency: 11x219MHz. The processor Vcore remained nominal in all cases, and we used the same boxed cooler for all our tests. The temperature values were measured with the help of the thermal diode built into the processor core. The core temperature was measured in two modes: idle mode and under maximum CPU workload created by S&M utility version 1.0.0 alpha.

In the idle mode the 90nm Winchester core is considerably cooler than the NewCastle core. However, under 100% CPU workload these two temperatures appear really close. At first sight this is a very unexpected result, I should say, because the 25% reduction of the maximum heat dissipation by Athlon 64 processors on Winchester core doesn’t seem to be affecting anything. However, there still is a logical explanation to this fact. The thing is that Winchester die not only started to generate less heat, but also got smaller in size. As a result, it has become a little bit more complicated to arrange proper heat dissipation from the die surface, than in case of a larger NewCastle core. This is exactly the reason why the core temperature does not characterize the core heat generation that much, but indicated the density of the heat dissipation streams, which appears even higher by Winchester compared with the predecessor. Therefore, Athlon 64 processors on the new Winchester core cannot boast a significantly lower temperature during active work.

The lower heat dissipation of the Athlon 64 CPU on the new 90nm Winchester core actually has a different effect. Namely, you can feel its influence by the cooler temperature. In Athlon 64 NewCastle based platforms the cooler warms up a lot and is warm to the touch. However, in case of Athlon 64 Winchester the cooler temperature gets significantly lower.

However, there are more facts proving that the new Winchester core of the AMD processors boasts reduced heat generation. Namely, we managed to measure the processor power consumption with the help of a multimeter. To get the value of the processor power consumption, which is the same as the processor heat dissipation, according to the energy conservation law, we actually measured the current going through the 12V processor circuit. In fact, this method is not very precise, because it doesn’t take into account the performance index of the processor voltage regulator circuit, however, it suits quite well for a preliminary rough comparison. Just like in case of temperatures measurements, we considered two situations: the idle state and the maximum CPU workload created by a special S&M utility version 1.0.0 alpha. The results of our experiments are given below:

The numbers speak for themselves. The new 90nm core consumes considerably less power than the older 130nm core in both: idle state and under heavy processor workload. Note also that the 50W power consumption demonstrated by the Winchester core at 2.4GHz core clock is a very low value for contemporary processors. This fact gives us some reason to hope that the frequency potential of the Winchester core will turn out pretty significant. For a more illustrative comparison we also measured the power consumption of the Pentium 4 processors based on Northwood and Prescott cores and working at 3.4GHz core clock. The results turned out simply impressive: under maximum workload Pentium 4 processor on Northwood core consumed about 100W of power, while the Prescott based CPU (with a C0 core stepping) required about 132W. This way, we have every right to call all Athlon 64 processors very economical solutions, and certainly this first of all refers to the new CPUs based on 90nm Winchester core.