I got my G4 933mhz in November 2003, and sure enough it came with built-in 128mb RAM. I had an extra 256 put in as a build option, and later upgraded that to a 512mb, giving me 640mb in total.
It is true that for a long time Apple were saying the maximum capacity was 640mb, but this is only because 1gb sticks were not readily available. Only a few suppliers did them (Apple wasn't one of them) and they were very very expensive.
I know several people who have installed third party 1gb sticks in RevA G4 iBooks such as ours and they work perfectly. I am considering it myself now the price has dropped significantly, but I am getting a new mac soon anyway, and to be honest, RAM is not a problem for me, it is the CPU and GPU holding me back.
It is true that for a long time Apple were saying the maximum capacity was 640mb, but this is only because 1gb sticks were not readily available. Only a few suppliers did them (Apple wasn't one of them) and they were very very expensive.
I know several people who have installed third party 1gb sticks in RevA G4 iBooks such as ours and they work perfectly. I am considering it myself now the price has dropped significantly, but I am getting a new mac soon anyway, and to be honest, RAM is not a problem for me, it is the CPU and GPU holding me back.