I have been using memtest86 and a custom built hardware testing image based on OpenSolaris, FMA and sun VTS for quite some time, and have had fantastic success with them. I just learned that the Linux kernel developers added built-in memory testing support to the Linux 2.6.26 kernel:
“Memtest is a commonly used tool for checking your memory. In 2.6.26 Linux is including his own in-kernel memory tester. The goal is not to replace memtest, in fact this tester is much simpler and less capable than memtest, but it’s handy to have a built-in memory tester on every kernel. It’s enabled easily with the “memtest” boot parameter.”
This is super useful, and will be useful when you don’t have memtest86 and company readily available. Nice!