My understanding is that AmigaOS is basically not great friends with SMP, because of the way that it works. For this reason, Hyperion are aiming at getting multi-processor support in without SMP - which is quite possible. I would imagine that they're aiming toward Aysmmetric MultiProcessing - which basically means (as far as I know - so please correct me if I'm wrong) that you have one processor core which does the system tasks, and farms out other tasks to other cores. Would people notice the difference between this and SMP? Probably not, especially on an OS as efficient as AmigaOS.
So, don't ask about SMP - ask about multi-processing, as SMP is just one type of multi-processing.
That's all my understanding - I don't know any more than anybody else... but that's what I've gleaned from the information around us.
What will it be like? No idea, but can't wait to find out!
