Processor Power Consumption
Like the Atom 230, the Athlon 64 2000+ does not have any extra power management functionality and therefore no Cool’n’Quiet energy-saving mode. There is no need for it, as the processor already operates on the lowest possible multiplier of x5 to reach a frequency of 1 GHz—Cool’n’Quiet would not be able to lower the frequency any further anyway. Furthermore, the Athlon 64 2000+ runs at 0.900 V, which is already lower than the voltage of other common models with Cool’n’Quiet activated. The Athlon 64 2000+, by our measurements, consumes only 4.3 watts.
If we manually set the core voltage to the lowest possible level of 0.800 volts (undervolting), the energy consumption drops from 4.3 watts to 3.7 watts under idle conditions.
Under full load conditions, AMD’s 8 watt Athlon 64 2000+ consumes roughly 7.2 watts. With the reduction in voltage, the power consumption drops further, down to 6.1 watts. With the reduced core voltage, the processor was stable during a test phase with Prime95 under full load conditions.
The Gigabyte GA-MA78GM-S2H we used in our test is equipped with 4-phase power. If a manufacturer optimized a 780G for low power CPUs and used a single phase, then the energy consumption of the Athlon 64 2000+ would be significantly lower.
We could not directly measure the energy consumption of the Atom processors, because the embedded board does not grant direct access to the 12 volt power line.