MacPro 12 core RAM configuration

[Bithero]

4 x 8

It's not with the 8GB modules you got lucky, but with the 4GB ones !
You should look into replacing the 4GB modules with one 8GB module to step up to 1066MHz.

Yes, that´s why I am happy to have now 4 of the same modules. with this setting they run with 1066 MHZ. I guess the limit here is the CPU and I hope they would run with 1333 MHZ if I would upgrade to a Westmere Hexcore CPU in the future. But frankly I don´t think it makes a noticeable difference in real world speed. But the amount of RAM is quite noticeable since I upgraded to CS5 (and I run in often together with Aperture 3.1) I had page outs even with
12 GB frequently, so 16 to 24GB is a realistic need and the 32GB are of course nice to have...