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 520W power supply units. The idle results were measured at the Windows desktop, and we used SMPOV and the POV-Ray renderer to load up the CPUs. In all cases, we asked SMPOV to use the same number of threads as there were CPU front ends in Task Managerso four for the Pentium XE 965, two for the Core Duo, and so on.
The graphs below have results for "power management" and "no power management." That deserves some explanation. By "power management," we mean SpeedStep, PowerNow, or Cool'n'Quiet. In the cases of the Pentium XE 840 and the Pentium XE 965, the C1E halt state is always active, even in the "no power management" tests. The Extreme Edition 955 and the P4 Extreme Edition 3.73GHz don't support the C1E halt state or SpeedStep. We have omitted the Pentium D 930 and 950 processors here because we don't have actual samples of these individual chips; our "simulated" versions with an underclocked Extreme Edition 955 are fine for performance testing, but not for power consumption.
The MSI motherboard we used to test the Turion 64 chips didn't set the voltage correctly, so we had to improvise. In order to assure that these tests were accurate, we manually set the voltage supplied to the processors using the RMClock utility. The ML series Turions were set at a peak voltage of 1.35V, while the MT-40 was set at 1.2V. All of the Turions were set to 0.9V when throttled down to their lowest possible clock speeds via PowerNow.
Under load, the Core Duo is running two threads here and producing an entire frame in roughly half the time of the Turion 64 or the Pentium M, yet its power consumption is nearly the same as the other mobile systems'. That works out to about twice the performance per watt from the Core Duo as from the Pentium M 760 or the Turion 64. Incredible. Intel has pulled off the same sort of feat that AMD did when going from the Athlon 64 to the X2 (witness the FX-57 and X2 4800+ numbers above), but Intel has done it inside of a much smaller power envelope.
For the record, notice that the system based on the Turion 64 MT-40 chip draws about 10W less than the system based on the ML-40. That's the same 10W delta AMD has assigned between those two CPUs' TDP ratings, although I'd have expected the difference to be exaggerated at the wall socket by power supply inefficiencies and the like. At any rate, the Turion 64 MT-40 gives the Pentium M 760 one heck of a run for its money in terms of overall performance and performance per watt, probably even more so than the ML-44 did in our recent comparison.
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