i'm running 1866 ddr3, stock. Lol!
A lot of CPU's wont even go that high fella, not without insane volts anyways.
In a very few games you can get a tiny performance increase with faster memory but it is a total waste of time and money.
You are far better off spending any extra money on a better GPU which will give a lot bigger increase.
Faster RAM can also have a negative effect of reducing performance slightly too in some games.
It was just out of curiosity to be honest, I was browsing OCUK and noticed 4200MHz kits and wondered if anything could actually use that amount of oompf![]()