Answer to "Can I upgrade my MAC PRO with another Motherboard or better CPU?"The answer is... it depends. First and foremost you should always provide the most important detail when you talk about "my Mac Pro"... as there are many iteration of such product you can't simply say Mac Pro without giving its model identifier (1,1 through 6,1 at the time of this writing) If you're talking of what makes the most sense (swapping a 3,1 motherboard into a 2,1 or 1,1 mac pro) then it sounds like mac pro 1,1 through 3,1 can indeed share hardware with some minor caveats and limitations. For instance a 3,1 has a faster memory clock speed (800MHz vs 667MHz of prev. versions) which means that when using the ram from an older model in a 3,1 motherboard it would run at lower clock speed since, even if the FSB on the 3,1 can run at 800MHz, the Ram will dictate the speed which will therefore be set at 667KHz (lowest common denominator) by those modules. One could also mix modules given that 800MHz ram can run at slower clock speeds... but for the above all ram chips will run at the lowest speed when...