Gradual FPS Drop in Fullscreen Only, Temps in check

Kian Palmer

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Jul 31, 2013
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Hello,

I've been having a problem in multiple games where my FPS drops over the course of about 15-20 minutes. It is especially noticeable in BF4, Overwatch, and GTA V.

I'll use Overwatch as an example here:

My uncapped FPS is about 130-135, and I cap the FPS at 120. After about 15 minutes of playing, I notice the FPS is now dipping below the 120 FPS cap and into the 100-115 range. 5 more minutes and it will move down into the 60-70 FPS range, and the game begins to stutter a lot.

Then I tried playing the game in Borderless Windowed mode. The FPS stayed up against the 120 FPS cap and never went down, however I noticed a fair amount of input lag.

This pattern exists in all games I have, for some reason it is worst in Overwatch, GTA V right behind.
I have checked my temps using HWMonitor and neither GPU exceeds 51C, and my CPU doesn't
exceed ~50C.

My question is, why does this happen in fullscreen and not borderless windowed? And how might I fix this issue?
I greatly prefer not to play games in borderless windowed because of the input lag I got.

Also, I feel that my system is underperforming. Some friends with GTX 1050 Ti's/1060's (who are getting higher frames) have effectively turned my computer into an AMD shaming target, haha.
But lets fix one problem at a time.

My system:
Intel i7-4790K watercooled @ stock clocks for troubleshooting
Corsair Dominator 16GB (4x4GB) 2133MHz C8
MSI Z97 XPower AC Motherboard
Samsung SM951 512GB M.2 SSD w/ PCI-E adapter
XFX R9 390X Crossfire (2) watercooled @ stock clocks for troubleshooting
Corsair AX1500i
Windows 10

I should mention that my copy of Windows 10 has yet to be activated; I haven't gotten around to buying a key.

Any help is greatly appreciated, thank you!
 

mitch074

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Mar 17, 2006
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I wonder if the inactivated Windows isn't to blame here: adding the watermark at the bottom of the screen after one hour may cause the frame buffer to be copied back and forth between the GPU and central RAM in a non-optimal way that will severely impede your system. In windowed mode, as desktop compositing is enforced, said watermarking may happen much more efficiently - and thus barely slow your system down.
 

Kian Palmer

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Jul 31, 2013
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Mitch I think you nailed it.
I noticed that if I restart my computer to get rid of the watermark, my framerate stays high, but I wasn't sure if it was because of the watermark or because of a fresh restart.
I looked up what desktop compositing is and it makes sense why games in windowed mode stay smooth.
Thank you for your help!
I have a question: when I play games in fullscreen, what causes the watermark bounce between the GPU and RAM?
 

mitch074

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Probably because the way a game renders in full screen is different from windowed - in full screen a game will seize control of the whole screen, while when windowed it would render to a subsurface that is then handed over to the desktop compositor for render. I would guess that Windows would forcefully grab control of the full screen by doing a video buffer copy, insert the watermark in it then copy it back to the video buffer, while inserting it in windowed would simply require a write directly in the video buffer - Windows having control of the screen wouldn't need to wrestle it from the application.
 

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