Power Consumption and Heat Dissipation
It is evident that it doesn’t make sense from the performance prospective to compare the CPUs with new and old processor stepping. Since Intel didn’t introduce any new technologies and didn’t make any architectural changes, CPUs with C0 and D0 processor steppings working at the same clock speeds will perform equally fast in regular benchmarks. That is why it is not very interesting to dwell on performance of the new Core i7-975 XE in our today’s article. However, the heat dissipation and power consumption measurements are, on the contrary, extremely interesting to perform. This is what we are going to do next.
First of all, we measured the temperature and full power consumption of the entire testbed (without the monitor) with both CPUs in idle mode, without any load. The tests were run with the CPU clock speed at 2.66GHz and 3.33GHz. We picked these particular settings because the first one is the nominal speed of the Core i7-920, while the second one – is the nominal frequency of the not announced yet Core i7-975 Extreme Edition CPU. During our tests C1E and Enhanced Intel SpeedStep power-saving technologies were enabled.
The obtained results indicate one thing: power-saving algorithms implemented in Nehalem CPUs with different processor steppings work almost identically. Both of them drop their frequency in idle mode to 1.6GHz, so we see almost the same temperature and power consumption. However, I have to say that Enhanced Intel SpeedStep technology works more aggressively by the CPU on D0 stepping. We saw the processor Vcore drop down to 0.912V under zero workload, while the CPU based on the old core dropped its core voltage only to 1.152V. Nevertheless, it barely affects the practical power consumption and heat dissipation readings.
The second part of our experiments dealt with thermal and electrical characteristics during maximum CPU utilization. We used 64-bit Linpack suite with LinX 0.5.8 shell. According to our tests, this combination warms up Nehalem processors best of all.
Processors power consumption and heat dissipation during stress-tests are no longer as unanimous as we have just seen in idle mode. New D0 processor stepping demonstrates evident advantage over the preceding core. The enhancements made to it provide a tangible improvement of the power consumption compared with the CPU on the old core version of up to 10-15W. Of course, the operational temperature of the CPU on D0 processor stepping also lowers.
So, despite all Intel’s claims, the CPUs on new processor stepping do have pretty definite advantages over the predecessors. They are more economical, which is a very good feature of the enhanced new core. Moreover, it should inevitably affect their overclocking potential, which we are going to check out next.