E-Prime Knowledge Base

5628 - E-Prime 2.0 Timing Data

Welcome to the E-Prime 2.0 timing Knowledge Base article. This article is dedicated to issues regarding critical timing using the E-Prime 2.0 software package. The data is presented by operating system and covers windows XP, Windows 7, Windows 8 and Windows 8.1.

E-Prime 2.0 millisecond accuracy

E-Prime 2.0 reports timing accuracy to the millisecond precision level. Although E-Prime coordinates with the operating system and external devices to continually have control of the computer's execution, the operating system or other devices can take control at any time, which will cause an experiment to be suspended while the operating system task is completed. When these instances occur, E-Prime continues to accurately timestamp so that post-analysis can filter the trials correctly.

E-Prime 2.0 and Operating System compatibility

As stated above, E-Prime reports timing accuracy to the millisecond precision level. For a full listing of Operating Systems that PST has thoroughly tested with E-Prime 2.0 for timing accuracy, please see the following Knowledge Base article: INFO: Operating system (Windows 8.1, Windows 8, Windows 7, Vista, and XP) support in E-Prime. What exactly does this mean? For example, in the RefreshClockTest experiment used to verify and evaluate subject station timing capabilities, an E-Prime 2.0 supported machine is likely to have a larger maximum missed tick, but less of them in comparison to the same machine running an unsupported version of E-Prime 2.0. Using the 1% rule, almost all machines that meet the system recommendations will be capable of collecting critical trial data. PST encourages all machines expected to collect subject data to run the RefreshClockTest to verify their ability to collect critical trial data. For more information, please consult the Critical Timing Chapter in the E-Prime documentation.

Verify subject data stations with RefreshClockTest

PST encourages all machines expected to collect subject data to run the RefreshClockTest to verify their ability to collect critical trial data. We have conducted thousands of timing tests on computers ranging from Pentium 60s - Pentium 500s with Pentium, Celeron, and AMD microprocessors on variety of cards and software methods. Our tests show that E-Prime 2.0 is accurate for millisecond precision timing. Windows takes over control of your computer at times to do operating system maintenance; this can be minimized but not blocked completely (remember the operating system has the highest priority). In our tests normal programs miss millisecond events much of the time (e.g. miss rates on a Pentium 60 of 58% and Pentium 500 of 43%). This means that timing via conventional programming reading a microsecond clock can be wrong at the millisecond level most of the time. We have developed and implemented within E-Prime 2.0, special timing systems that deliver high timing accuracy (e.g., our millisecond tick miss rate is down to 0.005% on a mid range Pentium 266, millisecond timing accuracy of 99.995%). Even more important, we have added a major innovation, Automatic Time Audit Logging, that records your timing precision in an easy to review/analyze method (e.g. mean display duration 109.4 ms, SD 0.49 ms). Using our Automatic Time Audit technology is likely the only way you can be sure of your timing accuracy without adding expensive specialized hardware. For detailed results of our timing tests and more information on what the results mean to you, please review Critical Timing and Appendix A - Timing Test Results located in the E-Prime User's Guide.

Timing Benchmarks

Not all devices are created equal. PST has undergone a number of timing tests with a number of PS/2 and USB keyboards and mice. Our preliminary timing tests have shown a wide range of variability between devices of the same class. Sound cards are even more prone to the same variability. Please check back to this section as updated timing benchmark results will be posted for the devices/machines that PST has tested. See the links below for some of the results we have found:

E-Prime 2.0 Stimulus Device Response Timing Values

The following is a table of average and standard deviation results for the timing test paradigms used by PST to determine device latency. The experiment presented a square stimulus in the middle of the screen for 100 trials. The refresh detector connected to The Black Box Toolkit accepted the stimulus which in turned fired a stimulus event 100ms later to trigger electronic components connected to the devices to mimic a human response. In addition to the 100ms delay value from when the stimulus was presented a 5ms value was subtracted from the received RT value because the experiment station was running at 100hz and the stimulus was presented in the middle of the screen. For example, if the RT value was 225.45, the actual RT would be 225.45 - 100 - 5 = 120.45.
The experiment used E-Prime in Fall of 2014. The Black Box Toolkit was used to collect and fire the response simulation values. The response box used was a PST Serial Response Box Model 200a. It was used connected via the UART COM port as well as using a Aten UC232A USB to Serial cable. Information about the paradigm used as well as specifics on the devices used or altered to simulate the responses and machines used to collect the data available upon request and intended to be posted to this timing site in future revisions. The same tests were run with an HP ZD7000 laptop running E-Prime 2.0 that collected the stimulus with a refresh detector attached to the SRBOX as well as simulating the response 100ms later. Unlike the subtraction for 1/2 the screen refresh, the latency values inherent via the SRBOX have not be subtracted from the E-Prime Timing Station tables which result in an approximate 2ms increase in the average values.
Since the original release of E-Prime in 2001, overall machine speed increases and enhancements have occurred in keyboard and mouse hardware technology to improve the average and stdev values of mouse and keyboard devices. The values reinforce that a device average and stddev values can vary between machine and operating system. In addition as outlined in "How choice of mouse may affect response timing in psychological studies" (Plant R.R.; Hammond N.; Whitehouse T, May 2003), the timing characteristics of exact model devices (e.g. as extreme as purchasing two Microsoft USB Intellimouse from the same vendor) can also have varying timing characteristics.

Dell Precision 490 - Windows 8.1

Response DeviceStatisticValue (ms)
Keyboard (USB Dell)Average4.82
Keyboard (USB Acer)Average15.02
SRBox (Serial Model 200a)Average2.38
SRBox (USB 2 Serial Model 200a)Average2.46

Dell i7 - Windows 8

Response DeviceStatisticValue (ms)
Keyboard (USB Belkin)Average36.86
Keyboard (USB Dell)Average11.35
Keyboard (USB Razor)Average17.14
SRBox (Serial Model 200a)Average2.23
SRBox (USB 2 Serial Model 200a)Average2.55
Parallel PortAverage0.33
Intellimouse USBAverage17.04

Gateway FX6850-51 - Windows 7

Response DeviceStatisticValue (ms)
Keyboard (USB Belkin)Average35.92
Keyboard (USB Dell)Average10.53
Keyboard (USB Acer)Average15.10
Keyboard (USB Razor)Average17.06
SRBox (Serial Model 200a)Average2.33
SRBox (USB 2 Serial Model 200a)Average2.27
Parallel PortAverage0.41
Intellimouse USBAverage17.08

Dell Precision WorkStation 340 - Windows XP

Response DeviceStatisticValue (ms)
Keyboard (USB Acer)Average16.20
Keyboard (USB Belkin)Average36.80
Keyboard (USB Dell)Average12.40
Keyboard (USB Razor)Average18.51
SRBox (Serial Model 200a)Average2.16
SRBox (USB 2 Serial Model 200a)Average1.53
Parallel PortAverage0.22
Intellimouse USBAverage22.04

Sound Startup Latency Tests

E-Prime 2.0 reports millisecond accurate timing. This does not mean that E-Prime 2.0 is capable of making hardware do things it cannot. For experiment paradigms that require auditory stimuli, much care and concern should be considered with the hardware being used. Sound cards can have good or poor startup latency, which is the time from when E-Prime tells the sound card to play sound to when the sound actually emits from the sound card or speakers. Not all sound cards are created equal. Results can also depend on the selected sound card driver and selected API (application programming interface). E-Prime 2.0.10.X allows for the option of selecting the DirectSound, ASIO or CoreAudio/WASAPI APIs so that the API with the lowest possible sound latency for a particular sound card may be used.

For more information on APIs in Windows 7, 8 and 8.1, please see this article: INFO: Sound Latency - Windows Vista / Windows 7 (and beyond). To determine the best API for your hardware, please see the chart below or use our Sound Tester program as detailed in this article: INFO: Use of SoundTester to determine machine compatibility with ASIO or Core Audio/WASAPI. Also, note that if the DirectSound sound startup latencies reported below are acceptable for a specific paradigm, the E-Prime 2.0 experiment's Sound device will not need to be configured or changed and the defaults may be used.

PST encourages using external equipment to determine the startup latency of your sound card. For our tests, we collected data using a Black Box Toolkit version 2 (BBTK v2) connected to a various computers. Each experiment computer generated a sound as well as a parallel port pulse that was detected by the BBTK's microphone and line in respectively. There were a total of 18 sounds and port pulses collected for each session. The experiment paradigm used white noise files that were set to 2 channels, 16 bit, and 44.1Khz. The parallel port pulse was sent at the start of the SoundOut object in the experiment paradigm. Since parallel port pulses have been shown to have extremely low latency, the receipt of this pulse represented the time that the sound was sent from E-Prime to Windows for processing. This was compared to the time that the BBTKv2 received the sound through the experiment computer's speakers. The difference in these two times represented the sound startup latency, that is, the amount of time that Windows, the sound card, and the speakers processed the sound before it was audible.

As a result of our tests for the various operating systems can be found on the charts below. Keep in mind that we have tested multiple sound cards and APIs on computers of varying functionality.

E-Prime Version 2.0 Sound Card Startup Latency Results

AdapterTypeMachineOperating SystemAPIMean (ms)StdDevMin (ms)Max (ms)
OnBoardOnBoardDell Precision Workstation 340Windows XP SP3DirectSound0.9310.0390.821.03
SB Xi-Fi PCIPCIDell Precision Workstation 340Windows XP SP3DirectSound69.562.4569.0986.54
SB Xi-Fi PCIPCIeDell Precision Workstation 340Windows XP SP3DirectSound69.1910.9766.9671.64
OnBoardOnBoardGateway FX6850-51Windows 7DirectSound44.537.2035.1584.73
OnBoardOnBoardGateway FX6850-51Windows 7Core Audio6.020.514.927.04
OnBoardOnBoardGateway FX6850-51Windows 7ASIO6.
SB Xi-Fi PCIePCIeGateway FX6850-51Windows 7DirectSound127.841.9522.0731.96
SB Xi-Fi PCIePCIeGateway FX6850-51Windows 7Core Audio28.241.9522.0731.96
OnBoardOnBoardDell i7Windows 8DirectSound44.505.6936.1074.16
OnBoardOnBoardDell i7Windows 8Core Audio6.260.855.157.41
OnBoardOnBoardDell i7Windows 8ASIO6.180.455.267.08
SB Xi-Fi PCIePCIeDell i7Windows 8Core Audio27.313.1621.8532.53
SB Xi-Fi PCIePCIeDell i7Windows 8ASIO17.100.4116.2817.80
OnBoardOnBoardDell Precision 490Windows 8.1DirectSound43.894.2634.6652.14
OnBoardOnBoardDell Precision 490Windows 8.1Core Audio6.260.974.627.99


The paradigm used on the E-Prime side was the SoundExperimentStation.es2 file. The sound devices were set at 2 channels, 16 bit, 44.1Khz. A white noise sound file was used. Event generation file used on the BBTKv2. The results are from 24 trials per subject/session.

  • E-Prime was used.

  • Hyperthreading was turned on all computers.

  • The MSCONFIG diagnostic mode was used to shut down background applications and services.

This topic applies to:
E-Prime 2.0

See Also
E-Prime 1.x Timing Data
TIMING ALERT: Machine configuration, design, or faulty components may result in bad timing data
INFO: Operating system (Windows 8.1, Windows 8, Windows 7, Vista, and XP) support in E-Prime

INFO: Sound Latency - Not all sound cards provide optimal millisecond timing
INFO: E-Prime Timing Information

This topic was created on:
Updated on 3/20/2015 2:51:00 PM (GMT)

This topic was last updated on:
Updated on 3/31/2015 1:41:00 PM (GMT)

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