from what i under stand the reason why we have to hack in tot he video cards is because apple decided to use the then unassigned pins 3 and 11 for their adc protocol

a few years later when agp 8X was released pins 3 and 11 were assigned to draw power

the older powermacs are looking for something on the newer cards thats not there

the psu's in macs are upgradable just dont ask how