MacInTouch Home Page: "With the recent spate of reported memory problems, how about reminding folks about the two great tools: (#1) 'memtester-2.93.1, and (#2) DCTest.
Memtest (as MacInTouch reported) is a port of the Memtest86 utility from the PC world (yes, Mac folks aren't the only one who can be tripped up by bad RAM -- intermittent or otherwise). Memtest of course checks most of your memory, but it also gives your CPU and registers a good workout along the way.
I did a Google search and found the latest info on memtest for the Mac at [Frisky's Home Page]. Even if you are not having problems, you should run memtest periodically ... and probably over a weekend. Be sure to read the 'READMEFIRST' doc.
The second utility, DCTest by Tim Seufert, does about the same thing as memtest, only for your disk and I/O subsystem. I found a place to download DCTest here (toward the bottom of the page): [Bad RAM]
Likewise, running DCTest over a weekend every once in a while is a Very Good Idea.
As to the '2GB limit' reported for Photoshop (and other apps), it seems this is due to OS X's loading shared libraries at just below the 2GB threshold. I believe this blocks malloc from 'seeing' RAM above 2GB, when the app first attempts to allocate RAM.
If anyone has better information on this '2GB limit' problem .. Please, please (including a date for a possible fix), please post it ! "