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Power Consumption in Real Applications

Now that we have introduced to you the processors to be participating in our today’s power consumption research and discussed the peculiarities of their power consumption during overclocking, it is time to move on to the next part of our session; power consumption measurements during work in real applications. We ran the tests in several typical modes:

  • Idle mode, when the system is under no operational load. In this case power-saving technologies kick in that is why the actual processor power consumption is minimal.
  • Maximum CPU utilization. In this case all processor cores are loaded to the utmost extent with Linpack 64 bit in LinX shell version 0.6.4.
  • Maximum system utilization. Besides LinX 0.6.4 that generates maximum CPU load, we also launched Furmark 1.8.0. This test has one special mode designed to stress-test the graphics sub-system.
  • Work in graphics editor program. In this case we launched Adobe Photoshop CS4 on our testbed and ran a script that retouched several 10-megapixel photographs.
  • Two-run transcoding of an HD MPEG2 video in 1280x720 resolution at 4 Mbps bitrate into H.264 format using x264 codec.
  • Final rendering of a 3D model in Autodesk 3ds max 2010 in 1920x1080 resolution.
  • Gaming load created by playing a popular Far Cry 2 3D shooter for about 5 minutes. The game was launched in 1920x1200 resolution with 4x AA and maximum image quality settings.

Each of the participating processors was tested in three most interesting modes:

  • Nominal mode, when the CPU worked at its default frequency with all power-saving technologies enabled. Turbo Boost technology was enabled for CPUs on Nehalem microarchitecture.
  • Overclocking without Vcore increase. According to our preliminary estimates, this type of overclocking is especially interesting for those enthusiasts who care not only about achieving maximum performance, but also about saving some power.
  • Maximum overclocking possible with an air-cooling system and relatively safe Vcore increase by about 0.10.2 V.

I have to say that during CPU overclocking for this part of our test session, we resorted only to raising the clock generator frequency and left the processor clock multiplier at its default value. We used this particular overclocking technique, because once you change the clock frequency multiplier Enhanced Intel SpeedStep and Cool’n’Quiet technologies stop working, because they are based on interactive adjustment of the multiplier. For the same reasons we set the voltages using relative settings, instead of absolute values, because in this case power-saving technologies are still capable of lowering the processor core voltage in idle mode. We disabled Turbo Boost during overclocking of Core i3 and Core i7 processors participating in our today’s test session, because as you should remember from our previous articles, it lowers the maximum stable CPU frequency.

As a result, during power consumption tests in real applications, we used the following system settings:

Unless indicated otherwise, the diagrams below show average power consumption readings of the entire system (including a mainboard, processor, memory, graphics card, hard drive and processor cooler with a fan) under different types of operational load.

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