Why 1600MHz instead of 1333Hz memories for i7-860?

[tofu1998]

Hi. I've read a couple of recommended set-ups online and come up with this question:

Why you guys use a memory with a rated speed of 1600MHz instead of 1333MHz to use with i7-860 which only support up to 1333MHz? Is this an overkill?

I'm looking into buy a kit of 2x2GB memories for P55-UD4P and i7-860. I wonder which memory will perform better in the real world (I don't over clock, but I'm willing to go to BIOS and adjust the memory timing):

1) 1600 MHz with 7-7-7-24
2) 1333 MHz with 7-7-7-21
3) 1600 MHz with 8-8-8-24

It seems that 1) is better than 3), but how about 1) vs 2), and 2) vs 3), all on i7-860 system without OC?

[RickyTick]

I may be totally wrong, but I understand that ram speed is determined by the motherboard and not the cpu. So with the proper motherboard, you can run 1600mhz ram. Maybe other motherboards are limited to 1333 ram. Maybe one of the tech-geeks around here can verify that.