SMP?

What SMP recommendations & experiences do you have to share?
I have a potential application for an x86 based solution.
How many processors are supported under QNX?
Any recommendations for standard SMP motherboards
that work with QNX?
Is it preferable to use Xeon rather than P3 or Celeronbased solutions?
Other hardware (e.g. not ATX format) recommendations?

Thanks in advance