Memory - Upgrading and Repairing PCs - page 356

Forcing the module could break it or the socket. Refer to Figure 6.14 for details.
10. Replace any cables or wires you disconnected.
11. Close the system, reconnect the power cable, and turn on the PC.
After installing the memory and putting the system back together, you might have to run the BIOS
Setup and resave with the new amount of memory being reported. Most systems automatically detect
the new amount of memory and reconfigure the BIOS Setup settings for you. Most systems also don't
require setting any jumpers or switches on the motherboard to configure them for your new memory.
After configuring your system to work properly with the additional memory, you might want to run a
memory-diagnostics program to ensure that the new memory works properly.
Troubleshooting Memory
Memory problems can be difficult to troubleshoot. For one thing, computer memory is still mysterious
to people because it is a kind of “virtual” thing that can be hard to grasp. The other difficulty is that
memory problems can be intermittent and often look like problems with other areas of the system,
even software. This section shows simple troubleshooting steps you can perform if you suspect you
are having a memory problem.
To troubleshoot memory, you first need some memory-diagnostics testing programs. You already
have several and might not know it. Every motherboard BIOS has a memory diagnostic in the POST
that runs when you first turn on the system. In most cases, you also receive a memory diagnostic on a
utility disk that came with your system. Many commercial diagnostics programs are on the market,
and almost all of them include memory tests.
When the POST runs, it not only tests memory, but it also counts it. The count is compared to the
amount counted the last time BIOS Setup was run; if it is different, an error message is issued. As the
POST runs, it writes a pattern of data to all the memory locations in the system and reads that pattern
back to verify that the memory works. If any failure is detected, you see or hear a message. Audio
messages (beeping) are used for critical or “fatal” errors that occur in areas important for the
system's operation. If the system can access enough memory to at least allow video to function, you
see error messages instead of hearing beep codes.
See Chapter 20 , “ PC Diagnostics, Testing, and Maintenance , ” for detailed listings of the BIOS beep
and other error codes, which are specific to the type of BIOS you have.
If your system makes it through the POST with no memory error indications, there might not be a
hardware memory problem, or the POST might not be able to detect the problem. Intermittent memory
errors are often not detected during the POST, and other subtle hardware defects can be hard for the
POST to catch. The POST is designed to run quickly, so the testing is not nearly as thorough as it
could be. That is why you often have to boot from standalone diagnostic media (normally an optical
disc or a bootable flash drive) and run a true hardware diagnostic to do more extensive memory
testing. You can run these types of tests continuously and leave them running for days if necessary to
hunt down an elusive intermittent defect.
Fortunately, several excellent memory test programs are available for free download. Here are some
I recommend:
• Microsoft Windows Memory Diagnostic —included with Vista and later
• Memtest86 — www.memtest86.com