PC Repair and Maintenance: A Practical Guide (Charles River Media Networking/Security)

So, how do you know when memory is a problem? First, if a problem occurs just after you installed new memory, you know that memory is a possible culprit. Other signs of a memory problem include frequent lockups (when the mouse pointer won't move and the Num Lock light on the keyboard is stuck on or off), or there is suddenly no video. Of course, neither of these symptoms is a certain indication of memory problems. There can be many reasons why these things could happen, such as viruses or corrupted Windows files. For more information, see Chapter 11, "Troubleshooting."

If you get memory error messages, especially early in the boot process, you might have a memory problem.

Memory Error Messages

Error messages are not always useful. Many are vague or cryptic, and some don't even represent a problem, while others are right on the money. It is also not always apparent whether the error message comes from Windows or from a program. This section will help you interpret memory error messages.

One type of error message that you'll be forced to heed is the type that appears early in the boot process and often prevents the computer from booting. Examples of these are the memory mismatch or memory parity error. They usually mean that the wrong type of memory is installed in the computer, incompatible modules are combined in the same machine, or that a module is faulty or not correctly installed.

If you see the following error message when attempting to boot the computer, the motherboard requires SPD memory for normal operation:

SERIAL PRESENCE DETECT (SPD) device data missing or inconclusive. Properly programmed SPD device data is required for reliable operation. Do you wish to attempt to boot at XXXMHz bus speed? Y/N [Y] Type [N] to shut down

Either non-SPD memory is installed, or the data in the SPD chip has been corrupted. You can continue to operate the computer, but you risk data loss. It is best to replace the module(s).

Sometimes, on Windows NT, 2000, and XP, you'll get a stop error, better known as "the blue screen of death." See Chapter 2, "System Configuration and Computer Hygiene," and Chapter 10, "Troubleshooting Internet Connections," for more information about these errors. There are other types of errors as well. Some of these can be memory related. In the case of stop errors, copy the exact text of the message (encompassing the long hexadecimal numbers at the top of the screen). Regardless of the type, copy the entire error message exactly and search Microsoft's Knowledge Base (http://support.microsoft.com) or on google.com for the problem. Make sure to either use quotation marks around the error message, or use the Advanced Search function to search for the exact phrase—and don't make any typos.

One common error message category is the out-of-memory error. A message might warn you to save a document because the system is almost out of memory. Often, these messages occur on systems with lots of memory and few programs running. These messages usually indicate a program error, not a problem with memory. If this happens, close the program. The error messages should disappear. Reopen the program and see if the problem returns. If the error messages recur, go to the developer's Web site or contact tech support (if possible) to see if there are any fixes for the problem.

Memory Testing Hardware

Available from companies such as CST (simmtester.com), these devices are the quickest, most efficient way to accurately test memory. They can usually tell you quickly exactly what is wrong and also locate the offending module. However, because they are priced in the thousands of dollars, they are cost-effective only if you are testing large amounts of memory every day. For this reason, small repair shops are unlikely to have them. If you need to have memory tested with one of these devices, you might be able to find a business, such as your memory supplier, that has one and will test the memory for you for a fee. Just make sure you transport the memory in an anti-static container and have the container marked to identify whose memory is in it.

Memory Testing Software

Memory-testing software doesn't have all the capabilities of the hardware testing devices, but the price is right.

Also from CST (simmtester.com) is a program called DocMemory. As of this writing, this can be downloaded and used free, although the Web site warns that this offer is for a limited time only. Make sure to download the user guide in PDF form, and then read it before attempting to use the software. If you don't read it and configure it correctly, the memory test could go on for hours, even days. This is a highly professional program, but note that the Web site might indicate that it does not work with all versions of Windows, although our tests indicate that it does work.

Memtest86 (memtest86.com) is also freeware, and is a little rougher around the edges than MemoryDoc, although it too will give you valid results. Read the readme file that comes with the zipped download before using.

Both of these are used in the same way: download and expand the zip file, and run the install program to install the memory test program onto a floppy. Then, making sure that the BIOS boot order is set to boot first from a floppy, restart the computer and run the program.

A diagnostic kit such as Micro-Scope (micro2000.com) and PC Certify (pccertify.com) is a great investment because it can not only test memory, but virtually everything on a PC that needs testing. Additionally, the available POST Card can be used to test the system even if the system won't power on. We discuss Micro-Scope and PC Certify in detail in Chapter 11.

Resolving Memory Problems

When you try any of the following, do so with the power off. If you change anything, test the system each time to see if the problem is resolved. Keep a list of each change you make so you don't have to repeat them.

First, make sure that each module is installed correctly. Then, remove the modules one at a time, making sure to continue to follow the rules of memory installation listed earlier in this chapter. If you are using DIMMs, try cleaning the memory contacts (pins) with a pencil eraser. Then, use compressed air, such as Blow Off to blow the dust out of the slot. Reinsert the module and try again. If none of these procedures helps, or if a memory test indicates a bad module, replace the module with a new one, and then test the system to make sure the problem doesn't recur.