I was given a G4 733 by a friend who has upgraded to an Intel Mac Pro and want to upgrade the CPU. I tried the Sonnet Encore dual 1600 but it doesn't work and the tech guy from the company I bought it from who fitted it doesn't know why. The have tried the CPU in another identical g4 733 and it works fine. The only thing I can think of is the ROM boot version which is showing as 4.3.3 f2 on my machine. The apple website says the latest version is 4.2.8. How could this be? I have tried to google the 4.3.3 f2 and there doesn't seem to be much info about it ....not sure why this should be. I could trade in the machine and have the tech guy swap the cards and stuff but I would lose all the music programes mt friend left for me if I can't use 4.3.3 f2 I think?Huh Any help would be appreciated!