VideoFX in dxnothing causes second vid card framerate drop
First my GFX/screen setup:
Screen #1(main stacked windows + some dxnothing windows) nVidia 670
Screen #2(dxnothing window only) nVidia 670
Screen #3(Non-isboxer stuff) nVidia 670
Screen #4(Non-isboxer stuff) nVidia 740
I have a 10-box setup with 10 stacked windows on Screen #1 with three dxnothing windows, two on screen #1 and one on screen #2. These are both driven by the same graphics card.
Everything works perfectly on screens #1-3.
With VideoFX enabled, however, screen #4 has a massive framerate drop and is completely unusable even for web browsing or the like.
If I run the dxnothing windows with all videoFX windows disabled, that monitor returns to a usable state. In any scenario, the first three screens are 100% fine, it's only ever the fourth monitor, which is on an entirely separate graphics card, that has issues.
The GPU load for this second card sits at 0% typically, but when I drag a window (anything; chrome, pidgin) onto this monitor it instantly spikes to 99% load until the window stops moving.
This started happening awhile back and I simply disabled the second graphics card, but now I'm running a 10th account and would like to get it back up and running.
It''s possible this started happening when I updated to Windows 8.1 from Windows 8.0. I have the very latest graphics drivers installed.
I at first suspected that it was a cross-GPU swapping issue, but all of my accoutns are stacked on the main screen, and the only thing leaving that screen (not even GPU) is videoFX through dxnothing windows.
Any ideas? I've tried setting up a new WIndow layout from scratch (needed to add 10th account anyway) but I have the same symptoms.