Intel Core i7: Nehalem Launched

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When idle, CPU-Z reported fluctuating CPU frequencies ranging from 1.6Ghz to 2.8Ghz for the Core i7 920, so the Power Control Unit seemed to be working somewhat mysteriously, possibly detecting slight variations in demand by the OS and responding dynamically with overclocking or underclocking. With Prime95 load, CPU-Z reported the CPU speed as 2.8Ghz, no matter how many worker threads were used. With only one active core, we were expecting a higher increase in clock speed, but that didn't happen. Turbo mode seems to be a crude way of saying "slightly overclock mode."

Minimum and maximum CPU states according to CPU-Z.

Task Manger, performance tab.

As the CPU supports Hyper-Threading, eight CPUs were detected by Windows. With Prime95 running four worker threads, the CPU usage of cores 0 and 3 hit 100%, while the other two remained idle.

Intel Desktop Control Center GUI.

Intel's Desktop Control Center is a beta application for adjusting and monitor system settings. It is available only on select Intel branded boards, so it is unfortunately, not an equivalent to AMD Overdrive. It does allow for a variety of settings to be changed from the desktop, though most changes require a reboot. CPU, memory, and bus settings can be adjusted and there is monitoring available for various temperatures and voltages via additional menus. You can also define presets for easy switching.

Overclocked to 3Ghz — minimum and maximum CPU states according to CPU-Z.

Using the Desktop Control Center, we briefly overclocked the i7 920 processor to 3Ghz by adjusting the CPU frequency to 150Mhz. The same CPU speed behavior that was in effect at stock speed also prevailed when overclocked: The multiplier shifted up and down, sometimes overclocking the CPU past its set speed. Running Prime95 with any number of threads resulted in 3.15Ghz according to CPU-Z.

It's hard to tell exactly what is going on under the hood as CPU-Z does not allow each core to be monitored. No software we know of tells whether inactive cores in a multi-core CPU underclock and undervolt or go to sleep.

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