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Intel Core i7-975 Extreme Edition Review

Power Consumption

For all of the performance tests, we disable all power saving technology in order to give us a consistent set of results, and also best-case performance numbers - even though technologies such as Intel's SpeedStep might only take microseconds to kick in, that can make a difference in some tests.

For Core i7 CPUs we disable SpeedStep, C1E support, Intel C-State technology and Turbo Boost (despite this being a default performance enhancement technology, it can make benchmarks unreliable). We would normally disable HPET too, but the Asus P6T Deluxe doesn't offer this. For Socket AM3 CPUs, we disable Cool'n'Quiet, C1E support and HPET.

However, for the power consumption tests we re-enable everything but Intel's Turbo Boost in order to get a real-world power draw.

Idle Power Consumption

For this test, we leave the PC doing nothing but displaying the Windows Vista desktop (with Aero enabled) for a few minutes and record the wattage drawn from the wall via a power meter.

Power Consumption, Idle

Power at wall socket. BIOS Defaults, all onboard hardware enabled. Windows desktop, Aero enabled, Id

  • Intel Core i7-975 Extreme Edition
  • Intel Core i7-920
  • AMD Phenom II X4 955 Black Edition
  • Intel Core i7-965 Extreme Edition
    • 128
    • 159
    • 130
    • 172
    • 136
    • 171
    • 138
    • 190
0
50
100
150
200
Watts (lower is better)
  • Stock Speed
  • Overclocked

AMD does fairly well with idle power draw - considering the 955 BE is running at 3.2GHz (the same frequency as the 965 EE) it doesn't really draw that much juice from the wall. The D0 stepping of the 975 EE and its resultant low VID helps to draw only 128W from the wall when idle - despite being clocked faster than the 965 EE, it also consumes less power.

Remember that the 920 we used in this test is the older C0 stepping, not the new D0 version. The Asus P6T Deluxe also refused to let SpeedStep kick in, so the 920 was locked at its full 20x multiplier, which hinders its ability to draw less power than the 975 EE.

Full Load Power Consumption

For this test, we run the small FFT test of Prime95 (v25.9) across all available processing threads and record the wattage drawn from the wall via a power meter.

Power Consumption, Load

Power at wall socket. BIOS Defaults, all onboard hardware enabled. Prime95 Load

  • Intel Core i7-920
  • AMD Phenom II X4 955 Black Edition
  • Intel Core i7-975 Extreme Edition
  • Intel Core i7-965 Extreme Edition
    • 211
    • 363
    • 218
    • 295
    • 245
    • 393
    • 257
    • 422
0
100
200
300
400
Watts (lower is better)
  • Stock Speed
  • Overclocked

Under full load, AMD still does well, with only 218W sucked from the wall compared to 211W from the Core i7 920. The 920 consumes shed-loads of power once overclocked though, while the 955 BE keeps its power draw down even when overclocked.

The D0 stepping of the 975 EE keeps its power down, so that not only does it run faster than the 965 EE, it also consumes less power. The D0 stepping is therefore much more power efficient than the C0 stepping of the 965 EE. Power efficiency might sound boring, but it reinforces our claim that for any given cooling method, the 975 EE is highly likely to overclock further than the 965 EE.