But 64 bit means also twice the data path and thus the possibility to process twice the data in parallel, doesn't it?
So I would expect roughly twice the performance of a 32 bit system and not only a few percent more speed.

But we also learned in the meantime that the G5 ran on OS 10.2.7. So there was no 64 bit OS running.
There is also the bottleneck of slow memory that could not catch up with the speed of the bus.
Michael