I too am now in the arena for changing out my power supply with an ATX mod. I found a website with various atx to Mac pinout diagrams for various g4 models... its atxg4.com There is a way to spare yourself endless cutting and soldering of harnesses; use a 20 to 24 pin ATX psu cable adapter. two pin slots on MY model of mac will overlap into open space on the motherboard but the harness fits nicely this way with almost all the color coded wires being in the right spot. From elsewhere on the net, cut a paperclip into two pieces, one end of each piece hammer-pounded flat and thinned on the wide edges to wedge down on either side of the pins inside the harness. Wires will then slide back out of the harness easily once you get the hang of the first one, means no increased resistance of soldered cut wires, and saves tons of time. Just redirect the colors into the right positions. Neater cleaner way of doing it. The only problem with MY particular model of Mac pinout, is that the author suggests a pair of 3a...