I just bought a GigaDesigns 1.8GHz 7447A processor upgrade for my G4 Digital Audio. If it's true that Tiger will see that card and refuse to install, I need to know, so I can sell my upgraded G4 Digital Audio and buy an iMac G5 at least... Straight from Apple: "Note: Mac OS X does not support processor upgrade cards. The amount of disk space required depends on your computer and the way you are installing Mac OS X." However, the word "support" could be a little misleading (I've learned that Apple can be a little sneaky that way sometimes ). It may just mean that Tiger isn't *designed* to run on upgrade cards and so Apple isn't responsible (or required to help troubleshoot), if it *doesn't* run on an upgrade card. Not specifically that it won't. Does anyone else concur?