G5 dual 2.5 only recognizes 7 gb ram

[dannyL]

Hi, I have a G5 dual 2.5. I loaded it with 8gb ram, but the system profiler only indicates 7gb. There are 4 pairs of 1gb ram cards and I have moved them around to ascertain that they are all in fact 1gb cards. But no matter what I put into the slots, Dimm6 and Dimm 7 always show 512mb.

I am running OS 10.4.11 and have just changed the 3.6v battery on the motherboard. I did a pram reset as well.

Anybody have any ideas?

I am truly stumped.

Thanks;
Danny

[Turboladdade]

First, try putting various combinations of only TWO sticks of memory into your G5 - one in each "bad" slot, and see if that changes how your computer recognizes them. I've often had confounding memory issues such as this wind up being the result of mis-matched memory sticks from different manufacturers that didn't play nice. It can also be one stick of our eight has some kind of corruption or failure that's messing up the memory "system" as a whole.

If you put two sticks, on in slot 6 and 7, and they're both correctly recognized as 1 GB, then progressively add sticks until they fail again. Then you'll find your culprit.

Are those G5 towers similar to Mac Pro towers in that the memory sits on it's own riser attached to the motherboard? If so, and the above still doesn't work, perhaps you have a bad memory riser? Otherwise, maybe you have an unfortunate hardware failure of the memory slots themselves.

[dannyL]

According to the manual, I have to load the Dimm sockets from lowest to highest. (0/1 - 6/7) I have made certain that all the chips are 1 gig chips. I have a pair of 512's, maybe I can load them in 0/1 to see if 6/7 can report 1 gig chips.
Thanks for the idea.

Hopefully it is not a bad memory slot or other similar issue.

I'll let you know.
Danny

[kriegvision]

Are all your 1GB sticks the same manufacturer and model?