Power consumption, as we all know, has become a very essential part of a CPU’s performance. Lower power consumption doesn’t just reduce power bills but also helps lower the cooling requirements for a CPU. A processor that consumes more power will require a stronger cooling system therefore potentially raising operational noise.

The following table shows the TDP (Thermal Design Power) of the processors we are benchmarking:

It is important to remember that the TDP values declared by Intel are not the true maximum power dissipation. Instead, they are the typical TDP the processor has
The AMD measurements, on the other hand, are the maximum TDP of the processor

In addition, AMD’s TDP might be slightly higher considering that the memory controller is integrated into the CPU. For Intel, the memory controller is external and instead integrated in the Northbridge.

To measure the consumption of the CPU we measured consumption of the whole system. In order to keep our results as accurate as possible, we tried to use exactly the same parts wherever possible, the exception being the motherboard difference between AMD and Intel CPUs. Here are the components:

• motherboard: Asus M2R32-MVP (chipset ATI Crossfire Xpress 3200)
• motherboard: Intel D975XBX2KR (chipset Intel 975X)
• memory: Corsair CM2X1024 6400 (5-5-5-15) @ 800 MHz; 2x1 Gbyte
• hard disk: Western Digital WD1600JS - Serial ATA - 7.200 rpm, 160 Gbytes
• video card: ATI Radeon X1950XTX (gpu 650 MHz; memoria video 2.000 MHz)
• operating system : Windows XP Professional, Service Pack 2
• video card: ATI Catalyst 6.10

The below measurements are for idle. For idle, we booted up Windows XP and tested the power consumption on an empty desktop.

The above test values are in watts. Also, keep in mind that it is the consumption of the whole system and not just of the CPU. Practically identical values came in for all AMD solutions while Intel solutions varied by each processor. For Intel solutions, the ones with larger L2 caches ending up consuming more power compared to those that had smaller cache sizes. AMD’s Cool’n’Quiet technology really helped reduce power consumption for AMD CPUs. By reducing the CPU’s clock down to 1GHz when idle, Cool’n’Quiet really helped increase power efficiency.

The above tests were taken with the system running at full load. Our tests were run while running a scene in Povray 3.7. As can be seen, the QX6700 came in with the most power consumption. This is expected because of the larger amount of cores. Unlike the other CPUs, the QX6700 has two physics die on the processor, whereas all other CPUs only have one.