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Performance Per Watt Normalized To 3.0 GHz And Pentium 4 630

Overclocking Intel's Wolfdale E8000
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Once again we'd like to look back at one of the first Intel processors that reached 3 GHz. The Pentium 4 630 wasn't the first one ever to reach that clock speed (that was the Pentium 4 3.0 GHz on socket 478), but it was the last 90 nm Pentium 4 generation for socket 775. If we look at the SYSmark performance per Watt of the 45 nm Core 2 Duo E8400 in relation to the Pentium 4 630, the performance per Watt result has increased by over 460%!

Diagram: Performance Vs. Power Consumption

Click Image to enlarge

The diagram requires some explanation. The x axis shows the time required to complete the entire benchmark, while the y axis shows the power required at any given point of time during the benchmark run.

The brown line represents the Pentium 4 630, which required almost one hour and 40 minutes. The purple line stands for the 90 nm dual core Pentium D 830, which finished in one hour and 32 minutes. The green curve represents the 45 nm Core 2 Duo Wolfdale, which took one hour and 15 minutes. Finally, the blue and the yellow lines stand for the Core 2 Extreme QX9650 45 nm quad core and the QC6850 65 nm quad core while the red line stands for the Core 2 Duo E6750. All of them took roughly one hour and 10 minutes to finish the benchmark.

The results may be confusing, as Wolfdale (E8400) should finish this workload quicker than its predecessor Conroe (E6750). And in fact it does finish the individual workloads quicker, as you could see in the SYSmark 2007 benchmark results in the benchmark section above. But we found that SYSmark 2007 often waits for system idle tasks to complete before it initiates the next workload. You can easily track this in the green curve, as the processor is clearly running idle after four minutes, after 25 minutes, after 50 minutes and again after one hour and five minutes. We repeated the benchmark several times and haven't found out why this happened, but we can conclude based on two facts that:

  1. E8400 does perform better than E6750 in the individual SYSmark workloads;
  2. E8400 achieves much better performance per Watt despite being idle for several minutes during the duration of the SYSmark test.
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