View Full Version : G5 256mb ram sticks not recognized

Oct 30, 2012, 06:29 AM
Why did I lose .5gb? Memory was 2.5gb as shown below. Then I popped in 2 more 1gb sticks for a total of 4.5 gb and now it shows 4gb instead of 4.5gb. It no longer recognizes the .5gb in J11 and J12.

Before adding another pair of 1gb sticks--

Hardware Overview:

Model Name: Power Mac G5
Model Identifier: PowerMac7,3
Processor Name: PowerPC G5 (2.2)
Processor Speed: 2 GHz
Number Of CPUs: 2
L2 Cache (per CPU): 512 KB
Memory: 2.5 GB
Bus Speed: 1 GHz
Boot ROM Version: 5.1.8f7
Serial Number (system): RM428ZHSQPM
Hardware UUID: 00000000-0000-1000-8000-000A95D4C0D2

Oct 31, 2012, 02:29 PM
Probably a compatibility issue, either the type of ram or because of the size of the ram and the way the mac buss is addressing it.

Oct 31, 2012, 03:13 PM
If that's the PCI version it can only take a maximum of 4GB. The PCI-X version can take 8GB. If it has 4 RAM slots, it is the PCI version, if it has 8 slots, it's the PCI-X version. They both have the same model identifier number, PowerMac7,3.

Nov 1, 2012, 06:08 AM
Probably a compatibility issue, either the type of ram or because of the size of the ram and the way the mac buss is addressing it.

To clarify, I did not touch the 4 sticks compromisising 2.5 gb, only after I added the 2 1gb sticks did it stop recognizing the 2 256mg sticks, mine is thePCI-X

Nov 1, 2012, 06:13 PM
I had a similar issue but after much trial and error realised the sticks had to be placed in certain slots (no doubt how the dual channel works) which I wrongly assumed was next to each other. Mine is a Late 2005 G5 DC 2.3.

I have two bank of 4 slots.
Each slot has a number (1-4 on both banks)
When adding memory in pairs they must be added as follows :-

Bank 1 Slot 1
Bank 2 Slot 1
Bank 1 Slot 2
Bank 2 Slot 2
etc etc

I added RAM recently by just putting them in the next two available slots and had less than before - took me a while with a torch and trial and error to work out what was happening...

Nov 1, 2012, 06:42 PM
Well, it dosen't make a lot of sense but I fixed by moving the 2 original 256mb sticks to the third slots of each bank, and moving my 2 1gb sticks to the 1 -or inside slot of each bank

Nov 3, 2012, 08:08 AM
Glad to hear you figured it out. I am having the same issue with mine. But keep an eye on it. I did manage to figure out how to get it to recognize the extra ram in my PM G5 but it lead to random crashes and random ram sticks failing during the boot diagnostic and the amount of ram the computer recognized kept changing. I think the fact that I am using several different brands and they are not all the same size even though they are matched pairs so I am still working things out on mine. I hope you don't run into the stability issues I did. I am back to it only recognizing 2gbs after some re-arranging but at least the computer is stable now.