Having all four DIMMs populated puts a little extra strain on the NB, but not much to make a difference if you're using the 9x multi. I tried it myself.
What's the Vdroop like on that board. What is the actual Vcore under load?
I pencil modded the board with a circuit writer pen, it works a lot better than a pencil, I tried a pencil and the vdroop didn't change one bit, using the circuit writer pen decreased the vdroop is about .008v - .030v, with it being ~ .008v 90% of the time, it very rarely dips to .030v and jumps right back up, the voltage actually jumps up about .012v as much as it drops .030v, but most of the time it's around -.008v, which is a huge improvement, these numbers are of course under load (IBT, Prime95, etc.)...
I'm not worried one bit about the RAM, there's a ton of overhead when I run it at a 1:1 ratio so it doesn't really need to be overclocked at all, plus the RAM I have isn't really very good OCing RAM, more importantly though I have mix matched sets of DDR2 6400, one set is 1.8v and the other is 2.1v, hopefully having the PI Blacks with a uniform voltage will let me push it further...
but the B3 stepping is a notoriously bad overclocker with most people only getting past the 3.00GHz barrier with elaborate cooling systems (watercooling, etc.), it's all good though, the gains from 3.00+GHz over 3.00GHz are pretty minimal...
I'll be happy if I hit 3.2GHz with the PI Blacks...
