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An External Stopwatch for Measuring the Timing of Events in a Computer or Distributed Computing Environment



Eric D. Simmon, Ya-Shian Li-Baboud, John V. Messina


The semiconductor industry continues to strive for improvements in the fabrication process. The Advanced Process Control (APC) systems supporting the fabrication process are steadily becoming more complex in order to deal with the high levels of automation and information management required to produce the next generation of semiconductors. Meeting the rising complexity challenges requires improvement in the performance of software and networks utilized within the factory. Information must flow expeditiously throughout the APC system within a well-defined period of time in order to maximize productivity. Towards this end, tools developed to accurately measure software and network performance in the factories are required to properly design and test new and existing APC systems. Measuring the time it takes for a piece of code to execute or the time it takes for an event to occur between two entities in a distributed environment is not a trivial task. Due to the virtual nature of a computer system, most conventional operating system provide no access to a reliable, real-time clock, and programming languages offer very little support for accurate time measurement. In addition, standard computer clocks can drift unpredictably depending on microprocessor load among other environment parameters. We propose and develop a system that uses an external calibrated data acquisition system and software-based trigger hooks to make this type of measurement. This paper will discuss the prototype system we built and some of the possible future enhancements. The system consists of a stand-alone computer with an accurate data acquisition card and data acquisition and analysis software (Figure 1). The acquisition system is interfaced to the device or devices under test through the serial port in the first prototype. Software triggers have been written which can be inserted around the programming code under test. These hooks have very low overhead and send a rapid signal with low latency to trigger an output at the serial port. The output is coded so multiple points can be recorded. To meet various measurement requirements several approaches can be taken to provide varying levels of measurement accuracy. The timer card used can have more accurate timing devices onboard. Due to the configuration of the data acquisition and analysis software, adapting the software to a new data acquisition board is simplified. The latencies attributed to the serial port can also be improved. One possibility is using the high speed of the USB port. Another approach, which may provide the lowest uncertainty, is to use a custom made PCI or PC Express interface card with hardware and drivers designed to provide the lowest jitter and latency.
Proceedings Title
AEC/APC Symposium XVII
Conference Dates
September 24-29, 2005
Conference Location
Indian Wells, CA, USA


Advanced Process Control, network, Semiconductor, time synchronization


Simmon, E. , Li-Baboud, Y. and Messina, J. (2005), An External Stopwatch for Measuring the Timing of Events in a Computer or Distributed Computing Environment, AEC/APC Symposium XVII, Indian Wells, CA, USA (Accessed June 17, 2024)


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Created September 23, 2005, Updated October 12, 2021