E2160 and E5200 fsb walls?

I have an E5200 that i've been trying to overclock lately. It has a good vid of 1.175 and it runs now at 333x9.5 3.16ghzz at 1.22v, probably lower. In bios it's set to 1.175, but the board adds 0.05 allways somehow, probably the board bios option of vid special add.

I tried OC to 400x8 with even 1.4vcore and pumped the NB core from 1.265 to 1.35v. It would not post. The board is a DFI LT x48 T2R.

Now my brother has a GA-P35-DS3, a solid board that you can't go wrong buying one. And the little E2160 it has, just runs at 1.35v 400x8 rock stable and no other tweaking.

I did get to 3.6ghz with my cpu and 1.28v, and will probably get to 3.8ghz with 1.35v, but I want to increase the fsb more.

So what am i missing here? Does the E5200 have a fsb wall of 333, while e2160 can go full? Last time i checked both Mobos support 1600mhz fsb (quad pumped) and even read a review on the DFI, and he testers wrote it can reach over 500 fsb with no aditional cooling.

Edit: Could the ram also be the culprit? They are geil ddr800 5-5-5-15 1.8v running 333/800 ratio also tried synchronous running at 333/667. While my brother has a set of patriots ddr1066.