In order to evaluate the performance of computer chips, it is necessary to run standardized tests on them that demonstrate what they can do. The ideal case is where a computer is to perform just one type of task all the time. In that case, it would simply suffice to test the processor by performing that very task under conditions just like those to be encountered in service, and the results would indicate just how good the machine would be.

In practice, things are never so simple—computers are typically applied for a variety of tasks, many of which cannot be known in advance. In order to still say with a reasonable degree of confidence what a chip can do in these unpredictable conditions, it is necessary to apply some ingenuity to the testing process. In order to perform measurements on chips, it is necessary to use...