x3900 (customer Water with 660 of radiator, I also tried with only 240), Ambient appx 75f
CPU: PBO +200 otherwise Auto, -0.05 offset on CPU and FSB set to 102.5
Memory: 64GB at 3066 (works at 3133, but is picky about booting), CAS16. Not very happy about this, but it is 64GB.
This leads to appx. all core 4200MHz in Cinebench, without the FSB it is closer to 4050MHz, in cinebench this does not make difference to temps in Prime95 it does a decent amount of temp.
Cinebench 20 scores:
240 and 660 are the around same appx 8300 multicore (first 2 passes tend to be closer to 8400)
Temps do differ: 240 appx 62c. 660 appx 55c This is running the test in a loop 10 times (manually Yuck).
While at it Prime 95, 2 hour avg temp:
240 appx 90c
660 appx 78c
The extra cooling in the loop definitely helps over long runs, short runs of Cinebench (1 or 2 loops), does not matter. Same with Prime95 normally takes about 3-5 minutes to begin to make a difference.
About radiator configuration: I have them configured externally using quick disconnects so I can move between 0, 480, 240 or 660 at will and location. 0 is only for testing the internal loop.