Thanks eva, but I have tried that... VTT from 1,21 to 1,45V, Vdimm from 1,55 to 1,71V, with all possible relations. I couldn't run LinX with 11GB of ram for longer than a few minutes no matter what. Not at close to 1600Mhz anyways. It does work at 190 BCLK with 6x dram.. 1150Mhz ram, no thanks.
Besides one shouldn't have to start tweaking switch values for a meagre 1600Mhz ram - I mean come on, that's even officially supported.