OCP on the HIS, once you raise the vgpu past 1.4v OCP kicks in and drops the voltage to 1.15v when you run 3D.I think that is what those extra couple resistors are doing when you compare to reference.
One thing you can try tho is a different BIOS. GeCube and Sapphire BIOS supposedly allow for more than 1.4v but I havent tried em personally. I always get the dam checksum error and am not sure how to change that.
Bookmarks