How to Troubleshoot the Worst PC Disasters

Memory Mayhem

DISASTER: You add a stick of RAM, and then your PC comes down with a case of the crashes. Sudden shutdowns, failed boot routines, and mysterious divide-by-zero errors can all be symptoms of a memory upgrade gone bad.

SOLUTION: You can remove the DIMM and go back to the earlier configuration, but if you need the memory capacity, a few things are worth trying.

1. Though it's rare, you may have a defective stick of RAM that needs to be replaced. To check, download and run Memtest86; it stresses and examines RAM to find errors that often don't appear during day-to-day use. We recommend Memtest86 for stress-testing your system immediately after any memory upgrade.

2. The two memory modules may have a timing mismatch, which you can work around by using the system Setup utility. As you boot the PC, watch the screen for a message indicating which key to press to access Setup; once you're in your PC's Setup utility, go to the memory settings screen. (You may find these settings under chip set features, but some PC Setup utilities may limit your ability to change memory configuration.) In the memory timings area, check the Column Address Strobe (or CAS) value. If it reads 2, change it to 2.5, then save the settings and reboot. That will add time for both modules to react to inputs from the system, though at a slight cost in responsiveness.

3. If that fails, underclock your system bus. In the Setup utility, find the settings for the frontside bus. Depending on your motherboard, you may be able to hand-tune the bus in 1-MHz increments. Drop the bus speed by 10 MHz or so. A caveat: Decreasing bus speed will slow performance.