Have you seen the Tiger requirements:
Hardware Requirements
Mac OS X v10.4 Tiger requires a Macintosh with:
* PowerPC G5, G4 or G3 processor
* Built-in FireWire
* At least 256MB of physical RAM
* DVD Drive
That puts all USB and CD machines out! I think it's more user friendly of apple to say firewire only machines than saying "machines over 400mhz" because some people just wouldn't know the speed of their computer AND this OS obviously needs more CPU power (the link being that firewire didn't appear really until 400mhz machines (with exception of B&W powermac)). However, the DVD drive thing is a bit dodgy.
Hardware Requirements
Mac OS X v10.4 Tiger requires a Macintosh with:
* PowerPC G5, G4 or G3 processor
* Built-in FireWire
* At least 256MB of physical RAM
* DVD Drive
That puts all USB and CD machines out! I think it's more user friendly of apple to say firewire only machines than saying "machines over 400mhz" because some people just wouldn't know the speed of their computer AND this OS obviously needs more CPU power (the link being that firewire didn't appear really until 400mhz machines (with exception of B&W powermac)). However, the DVD drive thing is a bit dodgy.