Need help with GPU Stutter whilst at 100FPS

[Mcmole]

So long story short, I have a I56600K and recently upgraded to a RX580 8GB model.

I play a few games and this happens in pretty much all of them most noticeably in overwatch.

If I have basically anything semi-gpu dependent, even something as little as playing a low quality YouTube video or having Wallpaper engine display a wallpaper on my second monitor whilst playing I get close to or the same FPS as if everything is fine, But its noticeably chunky and obviously dropping frames. to the point where its unplayable. I have to stop whatever I'm doing in the background just to have a smooth experience.

I'm only playing on a 75hz monitor so nothing fancy but thinking of getting 144HZ soon and it worries me that I can't multitask like I want to with serious lag.

 

So my specs are in my drop down, besides the changed GPU.  and a new 850watt Power supply.

Things of note.

 

GPU is maxed when playing 100% usage, however temps never hit above 80C

CPU sits around 50-60 usage. and under 70C at all times.

Ram usage sits just under 6 GB total with 2gb spare.

 

[ARikozuM]

You need more RAM and check your pagefile. 

[Mira Yurizaki]

If you're watching YouTube on another monitor, I've noticed that tends to screw with the syncing of the primary monitor. If the monitors' refresh rates are different, then it's probably an issue inherent in needing to sync both of them.