G5 Quad - 32GB possible?

[pc297]

I doubt it. There's probably a good reason why the slots aren't populated, and if my experience with server and workstation hardware is to be believed, it's because the unpopulated slots are tied to the also unpopulated second processor. Even if you were to populate all the board components to add the slots, odds are the slots won't be recognised due to there being no processor to see them.

You can likely see this in action by populating a DP logic board with only one processor and seeing how much RAM gets detected.

I have a 2.0 GHz DP with 4 DIMM slots/4 empty pads and I thought the question pertained to similar 1.8 GHz DP motherboards (which june 2004 G5 1.8 GHz powermacs are - M9454LL/A), from which SP 1.8 GHz G5 mobos are very different and don't have unpopulated DIMM soldering pads afaik (at least the ones with vertical DIMM slots and soldered in CPU, design shared with the 1.6 GHz, e.g. https://www.powerbookmedic.com/Powe...Board-for-A1093-Single-Processor-p-26046.html or https://harddiskdirect.com/661-3333...board-motherboard-for-power-mac-g5-a1047.html, while some SP 1.8 G5s do already have 8 slots see https://everymac.com/systems/apple/powermac_g5/specs/powermac_g5_1.8.html and https://www.thebookyard.com/product.php?manufacturers_id=12=Logic Boards&products_id=8381 - I doubt that the 4 extra slots are routed differently than on a DP motherboard as it's simply got empty soldering pads for the 2nd CPU - compared to some SP 1.8GHz G5s that are missing the 4 extra slots and second CPU, so likely all routed to CPU A e.g. https://www.thebookyard.com/product.php?manufacturers_id=12=Logic Boards&products_id=6716)? And disabling one CPU in OF via e.g. setenv boot-args cpus=1 should still get all RAM recognised on DP PM G5s with 8 slots on bootup afaik?

 

[Doq]

I don't know for sure; I only have a Quad in the lab. It was just a hypothesis based on experience with this class of hardware overall.

Perhaps G5s do have a different memory layout and only the first CPU is connected to RAM. Feel free to try this, though probably by physically removing one of the CPUs instead of disabling it in Open Firmware, just in case OF is doing some trickery behind the scenes.