Late 2005 dual core / quad core with PCI Express graphics.
When in doubt you can easily use Crucial Memory Selector or other vendors that will show available upgrades. There are also sites like Everymac.com and....
I had a similar setup - after searching on "slow G5" and seeing this thread, I pulled out the ECC, and the system seems much faster. It used to hang up quite a bit. Just try pulling the ECC out and seeing if it makes a difference. You hate to lose a GB, but my 3 GB system non-ECC only is faster than the 4 GB mixed was.
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OK to mix ECC and non-ECC RAM in Powermac G5?
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