Compare All Three Timers Drift Test with OEMIdle Periodic (Windows Embedded CE 6.0)

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1/6/2010

The Compare All Three Timers Drift Tests check for drift on the three clocks (GetTickCount, high-performance, and the real-time clock) by comparing them with each other. These tests periodically take data samples from the clocks. The system is kept in different states in the duration between taking the samples, allowing identification of drift introduced by specific functions.

To measure drift on individual clocks, use the Wall Clock and GTC Drift Test. These allow one to compare a given clock against a stop watch or any other external clock source.

A good way to use these Drift Tests is to run them to confirm the clocks do not drift relative to each other, and to run at least one of the individual drift tests to confirm that the clock does not drift relative to outside sources.

Ideally, one would compare the RTC, since this clock is not expected to drift with respect to outside clock. Test cases for other timers are included because it is often useful to be able to compare these clocks against an outside clock.

The RTC also has an automated drift test that compares it to an NTP server. If you have access to an NTP server, you can take advantage of this test; see RTC to NTP Drift Test.

Some platforms, for design reasons, have known drift in the GetTickCount clock. Take this into account when running the drift tests. The tests allow you to specify drift bounds so they will not fail when the drift is within known specified bounds.

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OAL Timer Tests