Using PC system timer to time software execution

Abstract

PC has a system timer which can be used to do software benchmarking (timing) or to time intervals during laboratory experiments. The timer 8253 4 which runs at 1·19318 MHz should theoretically be able to time intervals of 0·838095 μs at very high precision. In practice, its accuracy is affected by many factors including: interference from system memory refreshment, uncertainty in response to hardware interrupt and the delay caused by updating timer software. This paper is an attempt to evaluate the magnitude of these effects. The effect of the instruction prefetching and pipelining of 8088/80286/80386 processors is also discussed. It is found that in spite of its many limitations, the system timer can provide timing with a fairly high degree of accuracy if proper precautions are taken. © 1989.