I've got a 1600MHz CL7 kit here which works with the following on a C0/C1 i7 920 at stock CPU freq (for now) on a Gigabyte EX58-UD5: 10x RAM multi to get 1600 Vdimm 1.65V Vcore auto V-IOH auto V-QPI 1.34V All other voltages on auto. The kit works fine for 25 runs of LinX on max problem size, however when paired with a D0 stepping i7 920 on the same motherboard as the C0/C1 CPU, it refuses to run with the above voltages (errors within 5 mins). The kit, with the D0 CPU, will run at 1333MHz CL7 with Vdimm 1.5V and V-QPI 1.175V no issues. Am I missing anything? Do I need to adjust the QPI PLL too?