why not just use it intently?

compress a DVD or something... you can also buy memory test programs for OSX, cant remember the names....

I once had to work on a PMG5 with random freezes. Apple's service-provider-only testing utility passed the RAM after looping the tests for many hours. The only way I could reproduce the problem was to manually open enough stuff so that all the RAM was in use -- basically, I launched several pro applications, opened a bunch of images in Photoshop, and started running filters. I could get it to crash easily. It turned out to be one of only a handful of times I ever saw faulty Apple-branded RAM.

Anyway, the moral of the story is the best way to test RAM is to use it.

Maybe you were thinking of "memtest" ? It's free:
http://www.memtestosx.org/

Elixir and VDATA DIMMS are *not* compatible with G5's.

I have never found any third party stress test app for the macintosh. I would recomend winstress for windows boxes. However, you can have the computer play against itself in chess at the highest level of difficulty, play a dvd movie and type an apple works document all at the same time, just keep your memory and processor usage utilities up and running to. That way you can see how much of the processor(s) and memory you are using while doing this. If you have anything you can loop over and over (like a movie, or some kind of demo) keep those running as well. If the system runs mutliple things like that for several hours then I would say it passed the stress test.

The best way to test your memory is like Hayne stated above, the (free) app memtest:

http://www.memtestosx.org/

After having had a few bad experiences with faulty (non-compatible) ram dimms, I ordered new memory on www.crucial.com as suggested in previous posts. I must say I couldn't be more happy about their service! I ordered it yesterday around 1 PM and it arrived less than 24 hours later.

Memtest didn't give errors, so I guess my troubles are over. So my vote is for crucial, definitely.

I have not used this utility before. Does it actually stress the memory for bottle neck issues or does it just do a block by block scan on the memory? I have a ram testing machine in my shop where I can test memory outside a computer. I also have several bootable diagnostic applications I can use on computers to test memory. However, none of the memory tests I have do a stress test and do not test for bottle necking issues. Which is why I stress a machine when I first install ram.

I purchased my Power Mac with 1 gig from Apple, but anything more than that was too expensive. I ended up buying an extra two gig from Datamem.com and I have had no problems with it.

Here is their link for the Mac Mini...

http://www.datamem.com/viewcat.asp_Q_C_E_1168

Could someone please switch the Reality Distortion Field off ?

+Any+ RAM that is up to spec will do and it is even better to buy it from a reputable place where you are sure to get it changed should it be faulty.

It's just about soldering a couple of chips onto a not even mildly complex lil' board.

Depending on the circumstances you may be ready or not to pay a premium to get statistically slightly more reliable RAM but that's about it.

Proper antistatical handling and having spares handy for mission-critical machines will go a long way.

I jut bought a G5 (1.8 dual with 4 memory slots), it came with 2 samsungs dimms x 128, and bought elixir ram (2x512), I've installed that Ram, the finder info "about that mac" showed 1.25 of Ram. Fine.
I had a kernel panic. reboot. Then I had apparently 256 megs of Ram!...I've tried to swap the sticks. Then looking in the system profiler, I still had my 2x128, in the other slots 2x256, instead of 2x512.
So I took the ram back to the shop(by testing it,they've experienced the same amount of ram as I did), they've exchanged it, tested it on their g5, it showed up, fine...
I install the new ram (still elixir), boot up : 1.25 g ram... normal.
I've had a few more kernel panics, then couldn't boot...I removed the new sticks, left the original samsung from apple. Impossible to boot! swaped them...nothing!
Replaced them with the elixir...first my mac booted with the usual grey apple screen, then I saw all sorts of wrinting on that screen, I just remembered, that it said "hanging there" in the end.
Then I invert the two modules... it managed to boot without any problems, but still my memory is 512 instead of 1 Gig...

I mention also that I've been trying to re-install Tiger several times during these problems, and the installation process wouldn't complete, saying "error during installation, try reinstall..."

I've tried to find more info about these elixir chips, there seems to be a few problems with them... I'd like to get more info before sending them back to the shop again...
btw my stock "samsung" memory seems to be dead now...
thanks for any help!