I have a PowerPC G5 MacPro. The machine has 1Gb of ram. Recently the bottom ram slots stopped working. The computer now only recognizes the top slots and 512MB of ram. I have swapped the ram around, and all four sticks seem to be fine, just will not read in the bottom slots.
Your machine needs a new logic board., and quite frankly it is NOT worth having repaired. I had a USB port Go out on my G5 and the cost of having the logic board replaced was almost $1000. It is a spendy part.
I recommend putting the money toward a new machine.
There are no "technical solutions" to your "artistic problems".
Don't let technology get in the way of your creativity!