Let me begin by describing my setup. its definitely niche but that should be irrelevant.
I run an 8700k with SLI discrete gpu's output to 4 monitors in portrait mode. the first 3 are set up as a surround display, the 4th is an accessory display.
For the longest ive ran everything powered by the discrete gpus and had the igpu disabled. However as of late, a combination of a new central air unit, and having kids - ive become a little more budget conscious we'll say
For reasons that are again, not relevant - nvidia forces their driver to run the gpu at 3d clocks if >3 displays are connected. Even this could be rectified if you could connect your displays to "both" cards and still use Surround, alas this has been broken since 368.51 in june of 16 and I dont expect it will ever be fixed. At least not on this architecture.
So that left me with few options
1) no accessory display
2) no surround
3) very high idle clocks/energy wasted/heat
4) which is my current solution (use multi dispay power saver) which forces the clocks to p8 rest state based on defined paramaters (in my case, <10% gpu usage)
Then came the eureka moment. I could use the iGPU for the accessory display! So i quickly fetched a DP cable, enabled it in the efi, and installed the latest drivers. First issue was the nvlkkdm.sys (going from memory so might be #spelling) bluescreens. No matter which drivers I tried, they wouldnt get along. Also crashed outlook which was due to hardware acceleration. Forcing that off fixed the outlook issue - alas they still caused an nvidia driver crash.
At that point I decided to revert to #4 above, but keep the igpu enabled. I am watercooled so the additional heat isnt of consequence and it would be useful for using quicksync for this or that. I own several steam links and was having some issues with latest firmwares and the nvenc encoder so I wanted to try it.
Unfortunately, using quicksync also presented me with (slowly over a short time span) more and more artifacts until it crashed.
So again, with hopes it was a driver issue, I decided to for-go using quicksync for now and simply let it sit enabled so I had the option if i so chose.
This brings me to the issue which forced me to post. This ones the deal breaker.
As ive mentioned, I use an accessory display and SLI coupled with nvsurround. The latter forces me to game at a very high resolution which requires the use of SLI for acceptable framerates at acceptable settings. Because of technological limits which are unfortunately well above my pay-grade even after a decade in the market SLI does not function unless it has exclusive full-screen. The reason this matters is it would render my accessory display completely moot.
Fortunately several developers have come along and offer solutions which varying names. DisplayFusion+Prevent deactivation is the combination of software/feature I use. It forces the game window to keep focus when you alt tab, and allows you to move your mouse freely between the game and the accessory display. Amazing this can be done with third party software developed by a small company but.........ah nevermind, thats getting off topic.
So the short of it is - if i have the iGPU enabled, if I start a game and then use my accessory display, everything on it lags when I minimize or maximize it. Huge lag..
This is when the igpu is enabled in bios, enabled in device manager, but NOT physically connected to my displays. If i disable it in device manager (and presumeably the bios which is my next step should i not be able to fix this as its offering me 0 and causing tons of issues) the problem goes away completely.
If i re enable, it comes back. I can do this without even leaving the game and watch the issue come and go.
What im trying to understand is what/why or how its doing ANYTHING not connected physically to my display? Anything I can do about it?
Is it a driver conflict that may be related to the crashes I was getting when trying to power the accessory display off the igpu to begin with?
Am i stuck with igpu or discrete but both just simply isnt going to work?
Hope someone higher up the ladder can give me some suggestions or insight cause im all out. I apologize for the huge book but I imagine much of it was necessary/relevant.