By carefully selecting your test data and the order in which the addresses are tested, it is possible to detect all of the memory problems described earlier. It is usually best to break your memory test into small, single-minded pieces. This helps to improve the efficiency of the overall test and the readability of the code. More specific tests can also provide more detailed information about the source of the problem, if one is detected.

I have found it is best to have three individual memory tests: a data bus test, an address bus test, and a device test. The first two test for electrical wiring problems and improperly inserted chips; the third is intended to detect missing chips and catastrophic failures. As an unintended consequence, the device test will also uncover problems with the control bus wiring, though it cannot provide useful information about the source of such a problem.

The order in which you execute these three tests is important. The proper order is: data bus test first, followed by the address bus test, and then the device test. That's because the address bus test assumes a working data bus, and the device test results are meaningless unless both the address and data buses are known to be good. If any of the tests fail, you should work with a hardware engineer to locate the source of the problem. By looking at the data value or address at which the test failed, she should be able to quickly isolate the problem on the circuit board.