I have a Windows 7 Pro x64 system used as a home server.

Hardware: Core i5, 4670K (3.4 GHz) on an ASRock Z87E-ITX with the latest UEFI firmware.

I've discovered today that the CPU frequency is too high when the system is doing virtually nothing.

CPU-Z shows a CPU frequency of 3797 MHz. From time to time it drops to 3597 MHz. Multiplier always at 36-38.

Task Manager shows a cpu usage on Core 1 of 5-15%. Other cores are idle. All processes are at 0-1% cpu usage (almost all on 0%).

EIST and all C-States are enabled in the UEFI firmware.

When I change the power profile to power saver the multiplier drops immediately to 8 and the frequency to 799 MHz. But this mode is not an option, as when doing some CPU heavy work like packing using WinRar the frequency is at max 2100 MHz (and usually at 1200), so it's too slow. Additionally the LAN speed goes from about 95 MB /sec to 8 MB /sec (file copy).

If I go back to the Balanced power profile (with default settings) the CPU frequency goes within a second to 3797 MHz and stays there.

I have tried everything besides reinstalling Windows, and still have no idea what causes it.

I hope somebody has the answer why the CPU frequency is so high all the time.