Time Stamp Counter

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The Time Stamp Counter is a feature of the Intel IA-32 instruction set which is accessed via the RDTSC instruction. This was added with the original Intel Pentium processor.

Contents 1 Uses 2 Drawbacks 3 See also 4 External links

[edit] Uses

This is primarily used as a high-resolution timer.

[edit] Drawbacks

If the processor frequency changes (via SpeedStep for example) the timer no longer accurately measures wall clock time.

On symmetric multiprocessing systems the timestamp may differ depending on the CPU that is queried. In particular, AMD processors may have significantly different results. (See below reference by an AMD engineer on TSC drift.)

[edit] See also

• HPET (high precision event timer)

[edit] External links

• Using the Processor Clocks
• Programming examples
• AMD engineer on TSC drift in AMD processors