Thank you Bret, My MacPro have 5gb ram and Kona3 with Raid Sata.
Same configuration with Quad (G5) but with 4Gb ram.
Same scenario: V1 two clips (DVCPRO50) with distortion at -33.33, between these a cross dissolve. V2 Boris title 3D.
MacPro over trasition light green line (preview)
Quad (G5) dark green line (real time)
I have tried same scenario on Macbook Pro 17 with Aja IO: Light green light.
So I thing that FCP 5.1 is fastest on PowerPc for real time, fastest on intel for render.