[GD-Windows] Get exact CPU frequency

[Grisha S. <_g...@tu...>]

How can I get exact CPU frequency? I need it for timer which uses RDTSC
instruction. Currently I read '~MHz' value from
HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\0, but it
not exact - after 2 min running difference between my timer and GetTickCount
is 15 ms.