I have P4 loaded on a G4 desktop dual 450, OS9. Runs OK. I have P6 loaded on a G4 laptop at 1.67, OSX. Runs good, surprisingly... Most things run faster with P6 in X. But, oddly enuf some basic things run and work faster in P4 in 9. Go figure. Do check out the Mac forum here at RO. Good info and the Mac bunch is very helpful and responsive.