I have an older Powermac G4 867 DP MDD, bus speed 133MHZ, 256 MB SDRAM and a CD-RW/DVD-ROM. It works fine for me, but it's getting old, and I'm starting to work from home so it's critical that I have a working computer at all times. I'm planning to buy a new Mac, and use the 867 as a backup computer, but I also want to upgrade it. 1.) Will OSX Tiger work well with the 867MHZ processor? 2.) As for memory expansion, I moticed that the price difference between a 256 stick and a 512 stick is just $25. So why would someone buy a 256? And can I mix and match the 256 with a 512? Or would I be asking for trouble? If this is dumb to ask, or has been asked about a bazillion times before, I apologise, but I tried using the "search" function first. I've been using Macs since 1989, but I just use 'em, I don't know what makes 'em tick! Thanks!