As Floh said, it has only been tested with the G5 PCI-X. We switched to the G5 and 8.2 last year and it works great. We upgraded to Tiger, and that was a big problem, so we went back to 10.3.9 and all was fine. I believe you can install Tiger on the second drive, if you like, for apps other than M100. We did buy the Magma expansion chassis, and if you do, go for the QUIET model, which is only a bit more in dollars, but worth it. We popped in a second internal drive for media – Maxtor SATA 250 Gig – and everything has worked. We use firewire G-Raids for addtional storage. Make sure you install the newer Media 100 codecs as well. Media 100 HD was beyond our budget, but we chose to stay with M100 rather than go to FCP…just personal preference. Good luck!