Gradual loss in performance with Tri-SLI?

[DarkAngel_ZERO]

Hoping to find someone who may have run into a similar situation, but a short while back, I decided to give Tri-SLI a go, and added a new card to my system. Everything seemed fine for a time, but as of late, I've been running into a bizarre issue with my entire computer becoming nearly unusable after a gaming session.

What starts to happen as time goes on with whatever game I'm playing is that the framerate starts to fall gradually. I first noticed it with Warframe, which runs at 100+ FPS with no issue in most missions, but after about an hour or so of playing, that framerate starts to fall until it finally hits 10-20 FPS, even when sitting in the Liset cockpit. The real problem comes after exiting the game, with the Windows desktop suddenly running at the same speed. The mouse cursor moves at full 144Hz, but the desktop feels like it's stuck at 24Hz, and even trying to bring up menus can take a long time to open (if they open at all). At the same time however, there is no load on the CPU, no unusual disk usage, RAM usage is normal, and GPU usage is normal. Temps while under load have never exceeded unsafe limits (80C max on GPU 1).

At the same time, running intensive diagnostics and burn-in tests like Futuremark, FurMark/EVGA OC Mem 3GB Test, RealBench (30 min), and Prime95 all run without issue. I've run Memtest86+ for 5 passes and have had no issues there, and I recently reformatted my system and swapped out the RAID 0 840 Pros for a single 850 Pro, and still I have the same issue.

So long as I have the 3rd card installed, this has happened with every game I've played on my system, with some causing the issue much earlier than others (Civ 5 takes exactly 10 minutes of play between turns 200-250 to start exhibiting the problem).

Has anyone ever experienced anything like this? The only thing left that I can think of is that something might be building up and failing to discharge, leading me to wonder if maybe my PSU might be having difficulties with a higher power draw (The "recommended" PSU for a Titan needs 38A, and the HCP-1200 is 30A per 12v). Either that, or it might be a motherboard issue...

 

[n3zyd]

Is the cpu and/or gpu speeds normal when this happens? perhaps one of the video cards is getting hot and throttling then fails to come back up to speed. in windows on the advanced power settings tab is every thing set for High performance? because of power saving mode In World of Tanks I had an issue where in the garage my cpu would down clock itself then fail to resume normal speeds when the new match would start.

 

[DarkAngel_ZERO]

That's what makes this whole issue so strange. I kept a monitoring window open with EVGA Precision X and the Windows Performance window open when these problems started happening, and nothing appears out of the ordinary. Warframe barely reaches 65C under load on the primary GPU.

When I exit whatever game has caused the problem, voltages hardly fluctuate, the CPU goes down to idle loads, and the GPU downclocks normally after exiting a game, or at least, down to half-load clocks on the primary GPU due to my PG278Q. Power settings are set to High Performance, and tuned slightly with Samsung's high performance profile for the 850 Pro. For all intents an purposes, the computer itself sees nothing out of the ordinary, but the desktop responsiveness becomes a slideshow until the computer is restarted.