Using the Timer Latency Display Tool

The Timer Latency Display tool consists of:

A control and presentation application, which runs as an ordinary Windows task
An RTSS application, which performs the timing measurements

These two tasks communicate through shared memory.

NOTE: Source code for the Timer Latency Display Tool is included in the samples directory.

The RTSS task is similar to SRTM. The main execution thread creates an RTX timer, and sets it to expire periodically at the fastest available timer rate. The thread then enters a loop, testing a terminate request flag in shared memory, and sleeping between tests.

The timer function, which is called by RTSS each time the timer expires, reads the RTSS system clock, and computes the difference between the time observed, and the requested scheduled time. A histogram of this difference is compiled in shared memory. The RTSS task also accumulates shortest and longest observed latencies.

To run the Timer Latency Display tool:

Open Windows Explorer and navigate to C:\Program Files\IntervalZero\RTX\tools\LatencyDisplay.

NOTE: If you installed RTX to a location other than the default, substitute that path for C:\Program Files\IntervalZero\RTX.

Double-click NtRTSS.rtss to start the timer program. The program starts with the sound enabled.
Double-click the display program, RTSSDisplay.exe. You can change settings for sound and view while the timer program is running.

Timer Latency Display Options

Option	Description
Enable Sound	The timer function toggles the output state of the system speaker port each time it is called. Since the timer function is called periodically, this results in a tone with a period equal to one half of the timer setting value. The system timer is set to 1 ms in the demo, resulting in a 500 Hz tone.
Histogram	View the data as an accumulated histogram.
Latency	View a time sequence of minimum, maximum, and average values observed in a series of 1-second intervals.
Reset	Reset accumulated statistics.
Help	View Help information on the Timer Latency Display tool.

Other Actions

To end the program — Terminate the client process and then exit from the display process.
To end the display process — Click the X button at the far right of the title bar.
To terminate the timer process — Obtain the RTSS process ID and then kill the process by typing the following at a command prompt:

RTSSkill process_number

Where process_number is the ID of the process you want to terminate.