Have 6GB of RAM installed, "About This Mac" now says only 5GB.

[Rychy]

I just happened to look at the "About This Mac" thing this morning and noticed that it's only recognizing 5 of the 6GB of RAM I have installed.

Did one of the DIMMs die or something? I shutdown my Mac Pro and checked to make sure everything was installed properly. Booted up again and still only 5GB.

I'm guessing it has to be the Apple memory because the two sticks I installed were both 2GB. Is this something Applecare would cover?

[yellow]

Is it 3rd party RAM or "Apple" RAM?
You should read the Mac Pro manual on the Apple support site. There's a specific way that DIMMs have to be placed to have everything show up that's counter-intuitive.

[Umbongo]

Did you have 6GB before? Do you have the two 2GB DIMMs in the top riser in slots 1 & 2 and the 1GB DIMMs in slots 1 & 2 on the bottom? If one of your original Apple DIMMs has failed then it should be covered under Applecare. You should be able to get them to just send you another DIMM and send yours back.

[Rychy]

I know they're installed in the proper slots... for a month or two it showed up as 6GB.

2 x 1GB - Apple Stock RAM
2 x 2GB - Crucial RAM

I just checked the system profiler... it's saying that the Apple RAM is ok, but that each DIMM is only 512MB. I know that's incorrect. I have early 2008 Mac Pro.

[edesignuk]

Reseat the lot. Take a couple out, move them around. Just got to go through a process of elimination until you find a faulty DIMM or a faulty slot.

[rockinrocker]

yeah, that's what I had to do. Ended up having a faulty slot on riser B.

[Rychy]

Alright, I'll have to do some switching out when I get home from work.

[soldierblue]

Sounds more like the slot rather than the stick to me. If its a bad DIMM, it's probably not going to boot. As said, switch them around.

[SecondDealer]

Ram can become unseated over time, especially in notebooks but rarely also in desktops so just follow the above advice, It wouldn't make sense that half of both apple rams would have failed.

[nanofrog]

OP: If you have them out, you might want to clean them with a little rubbing alcohol (highest % you can find). Won't hurt. ;)

[Rt&Dzine]

Run Apple Hardware Test. The same thing happened to me after about a month of adding RAM. Turned out it was a bad RAM stick. The technician told me it usually happens in the first month or two, from the heat.

[Rychy]

Run Apple Hardware Test. The same thing happened to me after about a month of adding RAM. Turned out it was a bad RAM stick. The technician told me it usually happens in the first month or two, from the heat.

I ran the Apple Hardware Test, it didn't find any problems... but I checked the "About This Mac" after the restart and it's recognizing all 6GB of RAM again. :)

I don't know what happened, but thanks for all the replies. I appreciate this help.