From what I heard, yes it works, if you modify it. And if it's the 9600 Pro with ADC, the ADC port will not work after you modify it and put it in a G4.
-- Mac Pro Dual 3.0 Dual Core, 4GB RAM, 150GB Raptor HD, 500GB HD, Superdrive, Radeon X1900XT, Bluetooth, Airport Exteme, Logitech Z-5500 5.1 Speakers, 30" ACD
-- PowerMac G5 Dual 2.5, 2.5GB RAM, 160GB HD, Superdrive, Radeon X800XT, Bluetooth, Airport Extreme
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