Like the title says, I have a 6430 1366x768 HD4000 (not Nvidia) running 10.10.5 and Clover r3193 on BIOS A12 with screen artifacts. They look just like the picture in this post. Unfortunately, that thread was "solved" with the original poster replacing the motherboard I have also tried BIOS A16 and A11.
I believe I have the Clover setup configured correctly as I use the same setup (with appropriate DSDT/SSDT) on my 1366x768 E6230 HD4000 with BIOS A12 which works beautifully.
Before I re-load windows and sell the thing, does anyone have any suggestions of what I might try?