Severe stuttering of main monitor without loss of frame rate or lowered refresh rate.

adc · August 18, 2017

CPU: Intel - Core i7-4790K 4.0GHz Quad-Core Processor
CPU Cooler: Corsair - H75 54.0 CFM Liquid CPU Cooler
Motherboard: Asus - Z97-E/USB3.1 ATX LGA1150 Motherboard
Memory: Corsair - Vengeance Pro 32GB (4 x 8GB) DDR3-2400 Memory
Storage: Samsung - 850 EVO-Series 500GB 2.5" Solid State Drive
Video Card: EVGA - GeForce GTX 970 4GB ACX 2.0 Video Card
Case: Fractal Design - Define S ATX Mid Tower Case
Power Supply: Corsair - CX 600W 80+ Bronze Certified Semi-Modular ATX Power Supply
Operating System: Microsoft - Windows 7 Ultimate Full 32/64-bit
Monitor: Asus - PG279Q ROG Swift 27.0" 2560x1440 165Hz Monitor
Monitor: BenQ - XL2411 24.0" 1920x1080 144Hz Monitor

I'm not getting any error messages, but as I said in the title I'm getting some very strange display issues that seem to mimic the effect of a low framerate/low refresh rate on the monitor. I generally only notice this when putting some fairly heavy load on my system, though I'm not near actually pinning the CPU/GPU at 100%.

Usually around this time I'm doing a fair number of things; streaming to Twitch (I stream using NVENC at 1080p60, which doesn't use much of my CPU or GPU thankfully), playing League and listening to music through Youtube on Firefox. I also have a small bot written in Java (compiled using the latest version of Eclipse) that's connected to both my Discord server and my Twitch chat to ferry messages back and forth so I don't have to have Twitch chat actually open on top of just having Discord open.

The most confusing part of this problem to me, though, is that I don't have low FPS or a low refresh rate. The hardware FPS counter on my 279Q displays 144hz constantly, and my in game FPS counter for League never goes below 150~ FPS. I don't drop any frames on my stream, so it looks perfectly fine in the recording.

I have absolutely no idea what's causing this - it seems like sometimes it's caused by my network card starting to work (it's happened once or twice as a new youtube video loads), but it happens at other times too when my computer is just under a fair amount of load, not necessarily downloading anything.

I had another issue with my USB 3.0 ports on my motherboard not working because I had installed the drivers for the "regular" version instead of the USB 3.1 version of the board, so I installed all the drivers that the 3.1 version had to replace the other drivers. This seemed to help, as before I did this I could cause the FPS drops just by moving my screen around the League map very quickly, but it didn't completely solve the issue.

I ran a Memtest86+ for 3 full passes last night just in case, but there were no errors.

While under load, this is what HWMonitor displays as my min/max values over a 25~ minute period (note that the "current" values are just me watching a Twitch stream, not my load values):

https://puu.sh/xc1lP/4e1067b5ab.png

I know it does show that I hit 100% power usage on the GPU at one point, but it doesn't do that under the same load normally:

https://puu.sh/xc1yB/65fc96d954.png

So I'm not sure what caused it.

Task Manager places me at a solid 8.3~ GB of RAM usage, with 16GB free for use, and about 0.25% network utilization, spiking to 2.5-3% when loading a new song on Youtube.

Thanks in advance for any assistance, and please let me know if you have any questions or need more information.