Upgrading RAM in G5 Tower (Dual 2.0 PCI-X) from 4 to 8


macrumors newbie
Original poster
Nov 26, 2009
I was recently asked to upgrade the RAM in a G5 tower from 4 GB to 8 GB. My understanding is that while the G5s with PCI only allow upgrades to 4 GB, the PCI-x models (which were the top-of-the-range at each release) allowed up to 8 GB to be installed. This is one of the PCI-x models, so I bought 8 compatible 1 GB chips and chucked them in, expecting the machine to happily see them. But, it only recognised 4 GB. Funny thing is, I then had a look at the old chips I took out - there was already 8 x 1 gig chips in it, and it was only recognising 4 GB of them as well!

Anyone have any ideas why I'm only having 4 gigs recognised? Is that all this machine can take? Is it just recognising one of the 2 groups of RAM slots? Has anyone else had this issue?


macrumors 601
Dec 19, 2004
If your G5 has eight RAM slots then it should handle 8GB (the PCI-e models could take 16GB). I'm not 100% certain but I think only low density memory is fully supported. While only half of a high density chip is seen.

You likely bought high density chips as they are cheaper than low density ones.

You can buy proper chips for your G5 at www.crucial.com or www.macsales.com.
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