Up to 53% of the time spent on testing current Intel microprocessors is needed to test on-chip caches, due to the high complexity of memory tests and to the large amount of transistors dedicated to such memories. This paper discusses the methodology used to develop effective and efficient cache tests, and the way it is implemented to optimize the test set used at Intel to test their 512-kB caches manufactured in a 0.13- mtechnology. An example is shown where a maximal test set of 15 tests with a corresponding maximum test time of 160.942 ms/chip is optimized to only six tests that require a test time of only 30.498 ms/chip.