Random, unexplained FPS drop in late game

I'll have a solid 60 FPS for 70% of the game, but once it gets to thousands of units, suddenly something seems to change behind the scenes, and a max framerate of 30 FPS is suddenly enforced (with a janky framerate). There is literally no "transition", it just goes straight from solid 60 FPS to 30 FPS for the rest of the match (regardless of what is happening on the screen). This looks entirely like some sort of bug. Here is the graph of FPS to show what I mean -


This has happens in a few multiplayer games with a friend now. Any clues what could be causing this? He gets a solid 60 FPS throughout. I'm only getting 20% GPU usage and 60% CPU usage at the time of the drop. It seems to be independent of actual computer load, like it is just some flag that flips after X units are reached.

It looks almost like there is some code that says "if units > x, change framerate cap to 30 FPS". Make no sense, as nothing on my machine is bottlenecking from the looks of it.

Wow, this looks really strange ;-)

But I would be really surprised if something like that is somewhere in PA.

Anyway, can you attach a DxDiag?

But since this looks really strange, you might also check the list of software known to cause trouble:
http://steamcommunity.com/app/233250/discussions/2/558751813508748383/

The only software I have from that list is MSI Afterburner, but sounds like that is unrelated.

Is there any way I can PM you the DxDiag, I don't really like to post that sort of thing publicly (call me paranoid).

Just for reference here are some specs -

CPU - Intel Core i5 2500K
GPU - GTX 980
RAM - 16GB

All drivers are up-to-date, no other games have this sort of issue.

Does PA recover is you alt-tab out of PA and then back again?

Nope, since I had to alt-tab to get the screenshot of the FPS graph. Going back into the game, it was still at the strange 30 FPS cap.

If you only want PM DxDiag then send it to @DeathByDenim . He is the true wizard of support here.

In contrast to most games on Windows, which are using DirectX, PA uses OpenGL and a lot of features from OpenGL 3.1 and above. So other games running flawlessly are usually not a good indicator for driver problems.

From your description it really sounds like either a driver problem or a 3rd party program messing around with OpenGL swap buffers. I would suggest you try to disable MSI Afterburner and check if you can reproduce the fps drop. There is a FPS and performance display in game, you can bring it up by hitting Crtl-P a few times.

Ha, right, "wizard". You people are just too slow in replying usually, so I just hog all of the credit.

Anyway, ArmoredCavalry, if disabling MSI Afterburner doesn't solve the problem, you can try playing with the settings of the NVidia drivers. Things to try are vsync, forcing triple buffering, and setting Power Management to Maximum Performance.