After personally troubleshooting many hardware and software problems I've concluded the best and only reliable way to troubleshoot and rule out RAM is to remove all but one RAM DIMM (or pair of cards if your Mac requires two sticks) — try to duplicate the problem off your normal working install.

Swap each DIMM stick card SDRAM with another DIMM — leaving only one card or pair of cards installed at any time – until all your cards have been ruled out (each over hours/days of testing).

There are Ram testers links below, but removing the Ram and testing, as outlined, is the only definitive way to rule out Ram — so don't assume your RAM is good if it boots your machine or passes a software test routine.

It is hard to keep up with all the various warnings Apple uses in its machines to warn us of RAM problems, but here are some useful guides and tips.

Here is a how to official APPLE RAM GUIDE-MANUAL TO INSTALLING CONFIGURING REPLACING RAM in the Mac Pro (download PDF) Intel-based Mac computers.

So check to ensure RAM is installed properly, reseat memory cards FB-DIMM, and when ram is malfunctioning, check the Riser A and B boards (what the ram plugs into) for any red led lights. A red light here indicates a problem with the RAM.

RAM–related boot errors (sounds) breaking glass or musical beeps:
Apple TIL apple.com: 1–5 tones or breaking glass sounds on boot.

• 1 beep = No RAM installed/detected
• 2 beeps = Incompatible RAM type installed (for example, EDO)
• 3 beeps = No RAM banks passed memory testing
• 4 beeps = Bad checksum for the remainder of the boot ROM
• 5 beeps = Bad checksum for the ROM boot block

RAM–related boot errors (splash screens):

The boot tones or "built–in memory test failed" splash screen make your case in spades.

If you get the tones or failed–memory splash screens on boot, that's all you need say to make your point for warranty replacement — if the 'tech' wants to argue that point with you, find another technician.

The testers are not definative!

In fact, the only way to RULE OUT RAM is to remove it and test without it - but you may get lucky:

Adobe Photoshop engineer Chris Cox, wrote me (about the RAM testers):

"Ballard,
Timing problems are the biggest case that most test programs won't catch.
Yet applications will hit them maybe 1/10,000,000 times — which is often enough to cause problems.

"Also, testing programs are not using AltiVec or streaming cachehints — which change the memory access patterns.

"Testing programs also do most of their testing linearly through memory — which does NOT test rapid page (CAS) changes (which applications sometimes cause)."
Chris