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Power consumption
I'm a little disappointed in our power consumption testing because we ran into a big, hairy snag. This problem affected the previous Athlon 64 90nm tests we performed, although we were unaware of it at the time. It seems the CPU voltage option on our Asus A8V Deluxe motherboard isn't actually functional; we could set the proper voltage for each CPU in the BIOS, but no matter what, both the AsusProbe monitoring software and CPU-Z reported 1.6V for the CPU. It's possible this problem was caused by the revision 1008 beta 1 BIOS we were using, but that BIOS was necessary for compatibility with the 90nm Athlon 64. This problem was exacerbated by the fact that the A8V Deluxe is the only motherboard we had on hand that would POST with a 90nm Athlon 64 processor. As a result, all of the readings you'll see below were taken with the CPU voltage at 1.6V (although we did set the proper value on the BIOS for each processor). Generally, 130nm Athlon 64s are supposed to run at 1.5V, and the 90nm flavors expect 1.4V. Take the results as you will, or ignore them if they offend your precise sensibilities.

The Pentium 4 is more complicated, because voltage specs for Prescott processors are set at the factory and may vary from one CPU to the next. The general expectation is about 1.4V, and we used the closest manual setting on our Abit AA8 DuraMax mobo, which was 1.3875V. The P4 Extreme Edition 3.4GHz ran at 1.575V.

We measured the power consumption of our entire test systems, except for the monitor, at the wall outlet using a Watts Up PRO watt meter. The test rigs were all equipped with OCZ PowerStream 470W power supply units. Unlike our last set of tests, ambient temps in Damage Labs were down in the low 70s, much closer to a sane room temperature. The idle results were measured at the Windows desktop, and we used Cinebench's rendering test to load up the CPUs. For P4s, we used the multithreaded version of Cinebench to take advantage of Hyper-Threading.

Even with a handicap, the Athlon 64s consume much less power than the Pentium 4 Prescott chips. The battle at 90nm is worth a second look: the Athlon 64 3500+ pulls less power under load than the Pentium 4 550 does at idle. Yow.

That said, the Athlon 64 4000+ and FX-55 aren't exactly miserly when it comes to electricity. The FX-55 system pulls 190W at the outlet when it's really cranking, and that's without the GPU going full bore.