Hard drives aren’t the only parts of a computer that can fail. Memory modules, the central processor, the motherboard, the power supply, and all of the peripheral devices that allow the computer to exchange data with the rest of the world can stop working properly. Obviously, troubleshooting a memory module is very different from trying to fix a mouse or a keyboard, so this article contains specific advice about fixing many of the most common devices and components in and around your computer.

Memory Problems

Working with memory in older computers was easy: If the memory modules fit into the motherboard sockets, you could generally expect that the com- puter would successfully recognize and use them. Even if some of the modules were not identical to the others, the system would default to the slowest one and continue working.

But today, as computer processors and motherboards have become faster and more complex, adding more memory to your computer has also become more complicated. If all of the memory modules in the computer are not exactly the same, the system can become unstable and crash. Memory problems fall into several general categories: one or more of the physical memory chips mounted on a memory module might not be working properly, the memory modules installed in the computer could have different ratings, or the memory modules might not be compatible with the CPU or other components on the motherboard.

NOTE: You will have to open your computer and add or remove memor y modules to identify a damaged or defective memory module by swapping them and changing sockets. If you’re not happy about working inside the box, you can still run the Memtest86 diagnostic tests described in the following section to determine whether there’s a memory problem. If Memtest86 identifies a problem, let somebody with more experience repeat the Memtest scan and perform the physical repairs.

Identifying Memory Problems

The POST runs a quick memory test every time you turn on the computer. If the POST shows less memory than the amount installed in your com- puter, there’s at least one bad module in place. If you don’t know how much memory is installed in your computer, look in the General tab of the System Properties window (Start Settings Control Panel System). The amount of memory appears at the bottom of the list of system details. To find the bad module, turn off the computer, remove all but one module from the motherboard, and turn the computer back on. If the POST shows the correct amount of memory on the remaining module, repeat the test with a different module until you find the one that does not pass the POST. If the POST does not identify a problem, but you get a Blue Screen with a “memory error” code or a Stop message after Windows starts, the problem could be either a bad module or a conflict between modules with different ratings. For a more extensive memory test, download and run the Memtest86 diagnostic program from www.memtest86.com. Memtest86 creates a startup diskette or CD that automatically runs a series of detailed memory test scans to search for bad memory. If Memtest86 does not find any problems, then the memory modules are good, but a conflict between the memory and something else on the mother- board might be present. Try these methods one at a time to find and fix the problem:

Confirm that you are using the latest version of the drivers that control the motherboard. Go to the websites maintained by the manufacturer of your computer or motherboard to find and download the latest mother- board drivers. Look for a new video controller driver at the video card maker’s website. Update the BIOS to the most recent version available at the computer or motherboard manufacturer’s website. The same website should also offer a software tool for performing the update. Choose the default BIOS setting command (or Optimized Defaults set- tings), and save the new settings. If the computer has more than one memory module installed, try run- ning the computer with just a single memory module in place. If the computer appears to be stable, remove that module and try another until you have tested each module. If one module causes the computer to be unstable, that module is almost certainly the source of the prob- lem. If you have more than two modules, replace all the others and test the computer again.

If you have more than one memory module, try swapping sockets. Put the second module in the first socket and the first module in the second socket, and so forth. If all of the modules work separately, but not when they’re all in place, it’s possible that they have different speeds or different latency ratings (as reported by Memtest86), or the power supply is not compatible with your motherboard. If the modules have different ratings, try replacing them with modules that have identical speeds and ratings, or buy and install a single new module that has at least the same number of mega- bytes as the total of all the old modules. For example, if the computer has two 256MB modules, you could remove both of them and use one new 512MB or 1024MB (1GB) module. When you have confirmed that all of the memory modules in the com- puter have identical speeds and latency ratings, open the BIOS Settings menu and look for the settings (usually in the Advanced Chipset section) for CAS latency, tRCD (RAS-to-CAS delay), tRP (RAS Precharge), and tRAS (minimum Active-to-Precharge delay). All four of these settings should match the ratings for your memory modules, as reported by Memtest86. Don’t worry about understanding what these settings mean the important thing is that they match. Mismatched modules are sup- posed to default to the slowest setting, but sometimes they can produce Blue Screens in Windows. Find the BIOS setting for SRAM Frequency and confirm that it matches the speed rating of your memory modules. The speed rating is usually marked on each module and is reported by the Memtest86 diagnostic tool.

NOTE Latency is the amount of time that it takes a memory circuit to respond to different kinds of commands, expressed in clock cycles. The latency rating of a memory moduleshows the amount of delay for three or four command types, so a typical rating might be “2.5-3-3-7” or “4-4-4.” Lower latency rating numbers indicate better performance.

If you can identify a specific memory module as the source of your problem, remove it from your motherboard. If it’s the only module in the system, replace it with a new one with at least the same number of megabytes (MB). Look in the user manual for the computer or the motherboard, or the manufacturer’s website for information about the type of memory your system needs. You can also find tools that specify the right memory type for specific computers at these memory manufacturers’ websites:

www.corsairmemory.com/corsair/configurator_search.html

www.crucial.com

www.kingston.com

www.mushkin.com/doc/products/advisor.asp

www.pny.com/configurator

www.buffalotech/products/memory-configurator.php

If you have less than 512MB of memory in the computer, this is probably a good time to add more. Installing more memory (to bring the total up to a gigabyte or more) is the single least expensive way to improve your computer’s performance. Make sure the speed and latency ratings of your new modules are exactly the same as the ratings of the modules already in place. Also, try not to mix and match memory speeds, even if they are brand names. In theory, you should be able to do this, but I have had ugly Blue Screens caused by mismatched modules. If you discover that your memory problem was caused by mismatched modules, don’t throw away the modules that you remove from your computer. You might find a use for them in another computer some time in the future.

NOTE Look for a brand name (such as Kingston, Crucial, Corsair, Viking, PNY, or Mushkin, among others) on the module that caused the problem and use Google or another search tool to find the manufacturer’s website. Most quality memory module suppliers offer lifetime warranties, so you might be able to obtain a free replacement from the product support center. If your memory module is a “no-name” product, or if there’s a brand name on the label but you can’t find a website, it was probably cheaper than a brand-name unit because it didn’t include a warranty. As that old TV commer- cial for auto parts said, “You can pay me now or pay me later.”