Blackscreen issue on R290/R290x is mostly a low voltage GPU when switching from 2d to 3d or changin pstate. To resolve this issue you can lower RAM frequencies or pur +25mv on your GPU. It could be useful to edit video BIOS on r290 but actual tool like vbe doesn't work. I found that some skilled overclocker has edited BIOS to supporto more voltage for ln2 overclock or to mining... I tried to edit via hex editor but VGA refuse to start windows (BIOS digitally signed?). Any idea?