Articles: CPU

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Power Consumption

One of the most intriguing characteristics of the new Clarkdale processors is their heat dissipation. They are manufactured partially using 32 nm process, which should affect the practical heat dissipation. On the other hand, the calculated thermal design power claimed by the manufacturer is 73 W. and even though it is 22 W lower than the calculated thermal design power of Lynnfield processors, it is still higher than the TDP of Core 2 Duo CPUs featuring heat dissipation of only 65 W. That is why it is totally unclear what the situation looks like in reality: can we build an energy-efficient system with a Clarkdale CPU or dual-core processors on Core microarchitecture will still offer better performance per watt ratio.

Therefore we tested the actual power consumption of all systems participating in our today’s test session. 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.

In idle mode the power consumption of LGA1156 platform with a Clarkdale processor inside looks quite good. In this case it appears even more economical than an LGA775 platform. By the way, note that the total power consumption of fully-functional performance platforms is only a little over 50 W. We owe this not only to contemporary processors supporting efficient power-saving technologies but also to Radeon HD 5870 graphics card that is several times more energy-efficient than its predecessors in 2D modes.

Under heavy load the situation is exactly the same as we would expect it to be judging by the official TDP numbers. Core i5 and Core i3 based systems consume much more than systems with dual-core LGA775 solutions. However, their power consumption is not any higher than that of systems with quad-core CPUs. Pentium G6950 stands out a bit here, as it suddenly appeared even more energy-efficient than Pentium E6500 for LGA775 systems. Overall, we can conclude that power consumption of the ne processors correlates pretty nicely with their performance. Yes, they do consume more power than the previous generation dual-core CPUs, but their performance has increased dramatically.

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.

We are extremely surprised with the low power consumption readings taken off Clarkdale processors. However, the results can be explained easily. The thing is that the power from the individual 8-pin 12 V mainboard connector is sent only to the 32 nm processor die. The second 45 nm semiconductor die is powered by the mainboard. Therefore, we are also going to share the power consumption readings of the mainboards taken through their 24-pin ATX connectors.

Now everything seems to be in the right place. These extremely low power consumption readings taken off the 8-pin power connector on LGA1156 platforms are totally compensated by the high power consumption of the mainboard.

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