As hardware problems go, memory issues can be among the toughest to diagnose. Occasionally, your computer’s BIOS may flat out tell you that memory problems exist. But more often than not, you will have to find the problem on your own. This article offers five tips for diagnosing memory problems on a PC.

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1: Look for odd behavior

The first step in diagnosing memory problems is to look for strange behavior — things like lockups and blue screens — that might indicate a problem with the machine’s memory. For example, just last week I was attempting to make a configuration change on one of my machines. I was using a tool I’ve used countless times, but it kept returning error messages that made absolutely no sense. In the end, I discovered that the machine was having some memory problems.

Keep in mind that strange behavior alone does not necessarily point to a memory problem. The symptoms I have outlined can also sometimes be traced to problems with a CPU or a system board or even a malware infection. Even so, paying attention to odd behavior is a good first step in diagnosing a memory problem.

2: Run Memtest86

If you suspect that a machine might have a memory problem, I recommend running a free memory diagnostic tool called Memtest86. Unfortunately, memory diagnostic utilities such as this one are not perfect. Some of the machine’s memory must be used to run the tool, and that memory range can’t be tested. Furthermore, running a memory diagnostic tool usually requires you to shut down the computer you’re testing and run the tool from a boot disk. In spite of these drawbacks, I have had good luck with Memtest86.

3: Listen to the beep codes

One way to diagnose memory problems without opening the computer’s case or run specialized diagnostic software is to pay attention to the beep codes when you power up the machine. Since beep codes vary from one manufacturer to another, you’ll have to look on the manufacturer’s Web site to determine the meanings of any beeps you hear.

For example, some machines make one beep at startup to indicate that the machine is healthy. But some of the computers that use AMI BIOS don’t beep at all. If you hear a single beep on such a machine, it doesn’t mean that the machine is healthy. It usually indicates a DRAM refresh failure. So be sure you check the documentation for the machine you’re diagnosing.

4: Check the BIOS

Sometimes, you may not have to use diagnostic software or listen to beep codes. You may be able to look at the machine’s BIOS to see how much memory is reported as being installed. Not every memory failure will cause the BIOS to see less memory, but it does happen. Some BIOS will even go so far as to show you how much memory is installed in each slot. If you have such a machine, and it suddenly reports that less memory is being installed, you can look at how much memory is supposedly installed in each slot and use that information to quickly determine which memory module is causing your problem.

5: Use the process of elimination

Once you’re relatively sure that a memory problem exists, you have to determine which memory module has gone bad. Occasionally, you might run into a situation in which more than one memory module is bad. If this happens, you can still use the process of elimination to determine where the problem lies, but you will have to test each module individually. In most cases, however, only a single module goes bad at a time.

The first thing I recommend is to reseat all the memory in the system. I’ve seen quite a few situations over the years in which memory was merely loose, rather than bad. If the problem still exists after reseating, the next step is to begin using the process of elimination to determine which module is bad. Remove one memory module at a time (assuming that the machine does not require memory to be installed in pairs) and test the machine without that module. Through trial and error, you should be able to determine which one of the memory modules is to blame for the problem.