It’s a good idea to test your RAM before it starts showing signs of trouble, and MemTest from HCI Design is one way to do just that. MemTest is a freeware RAM reliability tester for Windows machines that tests the ability of your computer’s memory to store and retrieve data. MemTest tests the ability of your RAM to store up to 4 billion different unique bit patterns, as well as its ability to correctly hold those values over long periods of time.

How to use MemTest
To test your RAM with MemTest, you need to enter the amount of RAM the program should test. HCI Design suggests that you only test the amount of RAM that is free, rather than the total amount of RAM in your system; otherwise, your computer will spend 90 percent of the test time reading and writing to your hard drive, rather than actually testing the RAM.

To determine how much free RAM you have, check your current memory usage displayed under the Windows NT/2000 Task Manager or the Windows 9X System Monitor.

When I was ready to run the test on my Windows NT machine with 256 MB, I found that my programs were using over 128 MB of RAM. Since I was going to work on the computer during the test, I decided to test half of the free RAM, or 64 MB, as shown in Figure A.

Figure A

Even though MemTest is not able to check your entire RAM directly, because Windows dynamically moves the location of most of its subsystems, if MemTest runs long enough, eventually most of the RAM will be checked.

How long should you run MemTest?
In order to get a true evaluation of your RAM, HCI Design suggests that MemTest be run for several hours or overnight for the most rigorous testing. The longer MemTest runs, the better it will be able to identify RAM that is consistently corrupting data written to it. If MemTest runs overnight without detecting errors, it is statistically correct to assume that your machine can function for that period of time without making a single memory error, and it will more than likely be able to function without any memory errors.

If you cannot run MemTest for such a long period of time, you can still test for short-term errors by running the test until the status bar indicates around 4,000 percent to 8,000 percent coverage. If no errors are detected, your memory is most likely free of short-term errors. Testing for short-term errors will take around 10 to 15 minutes.

What to do if MemTest comes back with errors
If, during testing, MemTest turns up any errors, your RAM is faulty. HCI Design advises that you should replace your RAM immediately. However, if you have more than one SIMM/DIMM, MemTest will not be able to accurately pinpoint which particular chip is bad. In that case, you can isolate the faulty one by running the test with one memory board installed at a time.

How often should you run MemTest?
As a preventative measure, MemTest can be run periodically to test for both long- and short-term memory errors. It can be set to run overnight to test for long-term errors or while you are working at the computer to test your memory under typical processing loads. At the very least, MemTest should be run whenever you buy a new computer, install new RAM, or change your machine’s configuration (for example, when you overclock the processor). When running MemTest while you are away from the computer, I’ve found it runs much smoother with the screen saver turned off.

Where to get MemTest
MemTest can be downloaded for free from the HCI Design Web site. MemTest is downloaded as a zip file that installs entirely in its own directory; no changes are made to the Windows registry. It also comes with its own manual and free e-mail support.

MemTest is easy to install and use, even for those with limited knowledge of computer hardware. When run periodically, MemTest can alert your users to memory problems before it’s too late.

Is testing RAM worthwhile?

Do you test the RAM on your PCs? Do physical memory problems occur often enough to justify running a utility like MemTest? Post a comment to this article and share your opinion.