Timer Resolution in Windows NT

Last reviewed: September 25, 1995
Article ID: Q115232

The information in this article applies to:

Microsoft Win32 Application Programming Interface (API) included with:
```
    - Microsoft Windows NT versions 3.1 and 3.5
```

In Win32-based applications, the GetTickCount() timer resolution on Windows NT, version 3.1, is 15 milliseconds (ms) for x86 and 10 ms for MIPS and Alpha. On Windows NT, version 3.5, the GetTickCount() timer resolution is 10 ms on the 486 or greater, but the resolution is still 15 ms on a 386.

NOTE: The measurements in milliseconds indicate the period of the interrupt, not the units of the returned value.

The Win32 API QueryPerformanceCounter() returns the resolution of a high- resolution performance counter if the hardware supports one. For x86, the resolution is about 0.8 microseconds (0.0008 ms). For MIPS, the resolution is about twice the clock speed of the processor. You need to call QueryPerformanceFrequency() to get the frequency of the high-resolution performance counter.

NOTE: These numbers are likely to change in future versions.

Additional reference words: 3.10 3.50
KBCategory: kbprg
KBSubcategory: BseMisc

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Last reviewed: September 25, 1995
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