Set the uncore or whatever it's called to 200Mhz. 19x multiplier, plus Turbo mode which adds 2 more gives you 21x. 200 x 21 = 4.2Ghz. Memory on 8x gives you 1600Mhz
. There's another option in there somewhere which should be set to double your memory multiplier, ie, with yours at 8x this other should be on 16x. Can't check not cos I'm at work, but if you need any more help you can get me on xFire this evening
You should, if you haven't already, disable anything that saves power like EIST or C3, stuff like that. On most mobo's they won't work in Turbo mode anyway, but they can effect stability. Just make sure you leave CPU throttling on (often called CPU Thermal Protection).