Articles: CPU

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Power Consumption

Frankly speaking, we have no reason to expect the new processors on Piledriver microarchitecture to offer us anything new in terms of heat dissipation and power consumption compared with the predecessors. The manufacturing technology is the same for Zambezi and Vishera designs: both are made with 32 nm process. Yes, the semiconductor die in the new processors has been restructured in order to reduce its heat dissipation. But all the potential gained in this case was immediately invested into the clock frequency increase in the FX processors. As a result, the new Vishera CPUs have the same exact TDP as their predecessors. But this is just theory. What does reality look like?

To get a better idea of how greatly the processor’ energy-efficiency actually improved we performed a round of special tests. The new digital power supply unit from Corsair – AX1200i – allows monitoring consumed and produced electrical power, which we use actively during our power consumption tests. The graphs below (unless specified otherwise) show the full power draw of the computer (without the monitor) measured after the power supply. It is the total power consumption of all the system components. The PSU's efficiency is not taken into account. The CPUs are loaded by running the 64-bit version of LinX 0.6.4-AVX utility. Moreover, we enabled Turbo mode and all power-saving technologies to correctly measure computer's power draw in idle mode: C1E, C6, Enhanced Intel SpeedStep and AMD Cool’n’Quiet.

In idle mode all processors and platforms consume about the same power. In idle mode any contemporary processors will switch to special power-saving states, in which their power consumption will be very low – only a few watts. In this case the power appetites of other system components and the efficiency of the voltage regulator circuitry on the mainboard start to matter more and they partially mask the pure processor power consumption.

In case of single-threaded load AMD processors already start revealing their appetite for power. In this case systems built on these processors need about one and a half times more power than any contemporary LGA 1155 configurations. At the same time, the performance of AMD processors with this type of load is significantly lower than that of Intel processors. However, the new FX-8350 seems to have become a little more energy-efficient compared with the FX-8150.

Under heavy load the things are even worse for Socket AM3+ platform. In the end Vishera processor turned out even less energy-efficient than its predecessor, therefore the comparison against an LGA 1155 system based on a 22 nm Ivy Bridge processor end up really sad for AMD. In fact, even though Vishera’s performance sometimes made it seem like a very appealing product, the energy-efficiency aspect creates an insurmountable barrier between them.

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