As far as maximum addressing, the JEDEC 184 pin DIMM standard has 13 bits of column by row for 536,870,912 bytes in 8 byte blocks (2^26 * 8 or 2^29 bytes per bank). With 2 bits for banks, that allows a maximum of 2,147,483,648 bytes or exactly 2GB per device. I think that's the max? Which would mean without using a different memory type the memory max for the G5, ever, would be 16GB (drool) - as long as your power doesn't give out.
The power requirements of the memory might drain the life out of the computer first. The only power specs for the G5 I could find were max amp for a voltage rating: say 100 - 120 @ 6.5 amps. That's 650 - 780 intake watts, assuming about 60% efficiency (a consumer average) that's a 390- 468 watt power supply. Ok, a little beefy, but that's to be expected.
I can't find specs (I'm lazy) for the current DDR400 modules, but "Infineon now makes a 2GB DDR module. It requires 8.1 Amps @ DDR266" (
http://www.overclockers.com/articles696/) - so a guesstimate would be 8.1*8 = ~65 amps or about 150 watts of real power (at 2.2V). DDR 400 will be more of course (25-50% more).
So subtract about 200 for memory and the 50 or so watts on each CPU, 9 fans, control chips, HDD and you are quickly running out of available power.... hey doesn't the ADC connector provide power? That could be 70 watts right there!
😱
Maybe that's why they didn't put a second optical drive or more hard-disks - we'd need another 100 or so watts on the power supply pumping up the amps - and don't U.S. breakers trip at 10amps? We'd all need to stick a copper penny in the breaker just to run a G5.
😀
-Wyrm
