With some Mac users reporting that a recent Apple firmware download has disabled their RAM, Macworld Lab decided to see which third-party RAM might result in disappearing memory. The Apple firmware update checks out users' RAM; if it finds that the RAM's Dual Inline Memory Module, or DIMM, is out of specification, it will disable your memory.
We installed 10 different kinds of memory into a 400MHz Power Mac G4, and then ran version 1.0.5 of DIMMCheck -a free utility created by developer Glenn Anderson that lets you make sure your RAM measures up to Apple's specs before you download the firmware.
The result? Only one module-USA-DEM from Memory X-failed the DIMMCheck test. Here's a list of what we tested and how it fared.