Basically, my trifire setup works perfectly fine in most games (Crysis 3, GTA V, ACU, Battlefield 4, Dragon age Inquisition, etc) but Fallout 4 and the witcher 3 will ONLY use 2 gpus. I've tried doing a fresh install of the drivers and nothing. What's interesting about the witcher 3 is that although the 3rd gpu remains at 0% all the time, its memory clock and core clock are maxed out (unlike Fallout 4 where it is completely idle).
I am 99% sure that these two games support 3-4 way crossfire.
Is there anything I can do to force the games to detect my third GPU?
OFC, enabling AFR mode basically forces that (at the cost of massive flickering); but there must be another way for me to utilize all 3 GPUs. I know for a fact that there are people playing these games with 3/4 way crossfire.
Also, I had the same problem in crysis 3 (except that only 1 GPU was running) and I fixed it by doing a fresh install of the driver and changing the display to run off of the video card on the top PCIe slot.
Oh yeah and I'm playing in 4k (at 30hz right now until my cable arrives through the mail) with max settings and vsync and AA off.
i7 6850k @ stock
xfx r9 295x2 @1030 mhz core clock
msi r9 290x gaming @ stock (1030 mhz core)
32gb ddr4 G.Skill ram @ 2800mhz
120gb samsung 840 ssd
2tb Hard Drive
Evga g2 1300 watt
Not every game can benefit from 3 or 4 way Crossfire and it can even make performance worse in some cases or graphical issues (same for Nvidia SLI) so some games have it disabled.