Hello fellow blenderers!
I just unwrapped my new and shiny iMac 2,8 extreme and did some rendering tests. It seems that you can render faster if you set the threads to 4.
I repeated one rendering few times and here is my results:
10.27 - 2 threads
9.44 - 4 threads
10.34 - 2 threads
09.75 - 4 threads
those are like 10 seconds and 27 milliseconds or something.
So is there 4 cores in the new iMac extreme