G5 won't recognize new RAM

Try a PRAM reset. Hold down Command-Option-P-R when booting until the tone sounds thrice.

What model G5 do you have, what RAM does it have now, and in what slots? For example, if the existing RAM is in the upper and lower slots 1, the new memory would have to go in upper and lower slots 2.

Make sure one stick is in the upper slot, and the second stick in the same position but in the lower slots. ie. stick 1 is in upper slot 2, second stick should be in lower slot 2. Good way to see it is mirror it. And make sure that the ram modules are properly seated. Happened with me, but luckily I doubled check to see if I had properly secured the sticks in place. The tabs were in, but at closer inspection, the weren't completely set.

Did you lay the G5 on its side so you can push down hard enough for the latches to engage. See figure 7 of the instructions.

i would remove the RAM sticks in the "good" slots and re-insert with the new RAM sticks and see what happens. This would tell you if the RAM stick you bought are functioning.

If you heard a click, and the tabs are in, I think you should be okay. Keep in some sticks are higher than others. I have 3 different brands of ram in mine (x2), and they are all slightly different heights. But they all register fine.

If you feel that they are all seated properly, startup your system. You'll know if it's seated properly as soon as you see it registered in the System Profiler>Memory. If it's not seated properly, you won't see it. Shut down, and try re-seating it. Make sure that you have the knotch aligned correctly. These new DDRs only have one, compared to the older SDRAMs which have 2 (no way of botching that). And it doesn't help that the single knotch is only slightly off centre.

I may have the same problem...
I just bought two Crucial 1 GB sticks (DDR PC3200), and after installing them, the computer is not recognizing them.

I made sure to align the bottom notch correctly (as per Eric's instructions above). As I put in the sticks, I felt them come to a hard stop (I'd be afraid of breaking something if I pushed any harder...), but still the side tabs do not go all the way in, because they do not quite line up with the notches on the sides of the memory stick. Is it possible that Crucial memory puts the side notches in the wrong place?

If the tabs are not all the way in does that explain why the memory is not recognized, or are the tabs purely a mechanical feature to hold the memory in place?

Hi again,
I just checked the Crucial website and in the installation guide ( http://www.crucial.com/install/dimm.aspx) they make a point of telling you to push very hard to seat the sticks, and state that it takes 20lbs pressure to seat them...
I'll try again in the morning (after I've had my Wheaties)...
Ashwin

After reading your problem again, I believe we probably had the exact same thing. I have great news, though--my memory finally went down.

After reading the Crucial instructions (see my earlier post) I was more bold about the amount of force to use in pushing the sticks down, and I still couldn't get them down.

To check if the slots were in the wrong place, I ejected one of the original Apple sticks and compared the side of it to the side of the new sticks, and sure enough they were identical. At that point I decided to push even harder--it actually took an INSANE amount of force to get the sticks to click down--it was quite painful for my finger tips. If you guys have seen the instructional video on how to install memory on the OWC website, this was nothing like that. After sweating and applying a brutal amount of force, the sticks did finally pop down and the two side tabs clicked into place. When I booted the computer, the memory was there!

I would just caution you to make sure you're pushing straight down, because with that amount of force, pushing at any angle other than vertical would surely break the stick.

Good luck,
Ashwin

I wasn't sure exactly how much force you were using. But yeah, I had to push down pretty hard to get the tabs into place as well. A lot more than other times I've replaced or added ram to my previous systems.