Articles: CPU

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Power Consumption

We would like to wind up our today’s review of AMD Phenom II X4 965 processor on Deneb core with C3 processor stepping with the power consumption tests. As we have already demonstrated, the power consumption of this CPU in nominal mode is not very different from the power consumption of the similar processor on the previous core stepping. And it means that the new Phenom II X4 965 won’t compare against Intel solutions in energy efficiency. However, since we are focusing mostly on overclocking in our today’s review, we should also check what power consumption readings we can take off the 200-dollar CPUs during work beyond the nominal mode.

The following numbers show the total power consumption of the tested platforms (without the monitor). During our tests we used 64-bit LinX 0.6.3 utility to load the systems to the utmost extent. Moreover, to ensure that we estimate the power consumption in idle mode correctly we activated all power-saving technologies, such as C1E, Cool'nQuiet 3.0 and Enhanced Intel SpeedStep. However, I have to say that during overclocking only LGA1156 platform has all power-saving technologies intact. Other two platforms do not let overclocked processors to lower their core voltage in idle mode if it has been increased during overclocking.

Here I only have to say that during overclocking we increased the core voltage of both Intel CPUs to 1.4 V and that of the AMD processor – to 1.575 V.

When there is no tangible load in place the difference in practical platform power consumption becomes very noticeable. The most economical is Core i5-750 that can switch to fully-fledged energy-efficient states even after overclocking with Vcore increase. The power consumption of Socket AM3 platform with the installed Phenom II X4 965 CPU on new processor stepping is beyond any criticism: overclocking increases its power consumption quite seriously, which makes it consume in idle mode just as much as other mainstream platforms would under heavy operational load.

And although during overclocking to 4.0 GHz the maximum power consumption of Phenom II X4 doesn’t increase as much as the peak power consumption of systems on overclocked Intel CPUs, it still remains the least economical overclocker solution.

To get a better picture of the situation we also tested the power consumption of our testing participants under heavy load without taking into account the rest of the system components. To be more exact, we measured the power consumption along the 12 V power line connected directly to the processor voltage regulator on the mainboard and along the mainboard power lines.

High power consumption of the AMD processor is no longer a secret to anyone that is why we first of all wanted to draw your attention to the relative increase in power consumption of any overclocked CPUs. Overclocking raises the energy appetites of processors, which you should definitely keep in mind when shopping for power supply units and CPU coolers. For example, 50% overclocking of Intel processors results in almost doubling of their power consumption. With Phenom II X4 things are a little better: at 4.0 GHz frequency this processor consumes “only” 75% more than the same CPU at 3.4 GHz. Nevertheless, in absolute numbers its power consumption reaches shocking 250 W.

In addition we also measured the mainboards power consumption. The thing is that LGA1156 and LGA775 platforms use the power sent to the board along the 12 V power line for the processor cores. Uncore part of the CPU and the memory are powered from the mainboard via 24-pin ATX power connector. That is why the mainboards power consumption is worth checking out.

However, the revealed results can hardly change anything in the shaped up general picture. The mainboards power consumption doesn’t increase significantly during CPU overclocking, even on LGA775 or LGA1156 platforms. As for Socket AM3 mainboard, it consumes practically the same amount of power in nominal mode and during CPU overclocking.

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