This function NOT obtain the CPU frequency (or CPU speed). This function is to get the frequency of the high resolution timer counter. Timer counter value is obtained with QueryPerformanceTimer()

Technically this article, and the community comments are correct, this function does query the frequency of the CPU. but only in so far as that 99.9% of current CPU's available operate at the same frequency as the Performance timer component within. However, you must remember you are querying for the frequency of this timer, not the frequency of the actual CPU.

I myself (on an Intel Celeron Mobile based machine) have noted on occasion that the CPU frequency reported in tools such as CPU-Z is different to the frequency reported by this function call. This is especially true when using Intel Speed Step, or when the BIOS has been set to use CPUTHRM settings to throttle down the CPU when overheating.

In these latter occasions is common to see a higher return from "QueryPerformanceFrequency" than one can see reported by the CPU. Skewing any timing performed in a high performance loop.

Apparently this function can be used to retrieve the processor speed,is it correct ?

arabcoder

[DllImport("kernel32.dll", SetLastError=true)]
public static extern bool QueryPerformanceFrequency(out long lpFrequency);

<DllImport("kernel32.dll", SetLastError:=True)> _
Public Shared Function QueryPerformanceFrequency(<Out> ByRef lpFrequency As Long) As Boolean
End Function