I have XSI 7.01 on a MacBookPro (2,33 GHZ / 2GB / 1 Dual Core / Windows XP 32bit SP2-Boot Camp) and on a Mac Pro (2,8 GHZ / 4 GB / 2 Quad Core / Windows XP 32bit SP3-Boot Camp).
For my testrender I used a simple scene with a room, a spotlight which shoots out 750.000 photons for global illumination rendering.
The MacBook Pro rendering time is 7.43 sec
The Mac Pro rendering time is 1.65 sec
That’s not surprising isn’t it 
But now the strange thing:
The MacBook Pro is using 10 sec for shooting out the 750.000 photons but
the Mac Pro is using 52 sec for shooting out the photons.
So, why is this happen?
Bert