Drops to 59 fps when capped at 60?

[Azakius]

Wondering if someone can help me. 

This isn't really an issue, more of an observation that I'm just curious about. I'm playing Rise of the Tomb Raider, I've capped my fps to 60 at 1440p max settings and I'm hitting it, I can even get over that, but don't see the point putting the stress on the gpu. How come occasionally the fps counter drops to 59, despite being able to get 100+ if I were to uncap fps? Is this just normal for displays to do this? 

 

Thanks for any help! 

[AMD A10-9600P]

That's normal, nothing to worry about there.

[SleepingGiant]

Maybe the scene being rendered is intense or fast phased compared to other scenes

Like the GPU is just chilling then its suddenly hit with a huge load, it might take some time so process it?
Dunno exactly what's happening but this is my theory

[Eigenvektor]

That's a side effect of capping, because you can't do that super precise.

 

In order to run at a fixed 60 fps, every frame has to take 16 2/3 ms. If your CPU/GPU are fast enough to take less time, you "cap it" by "sleeping" the remaining time. So e.g. if the frame is done after 10 ms, you now sleep for 6 2/3 ms before rendering the next frame. If there's a slight variation you end up with 59 instead of 60.

 

And yeah, if the next frame suddenly takes 18 ms to render you can't get the time you spent doing nothing back.

[Nathanpete]

Not the display at fault, but the software limited framerate causing a small sync issues that causes a frame to be delayed by an itty itty bit, meaning that in the last second, only 59 frames where displayed. This is assuming you are using a framerate counter that counts how many frames were rendered in the last 1000ms and not the frametime of the last frame, which then uses basic math to come up with the instantaneous framerate at that given moment. 

 

For example, using net_graph 1 in CS:GO produces a ovelray in the bottom right corner, and the very first number is the instantaneous framerate, which is calculated by taking 1000 divided by the number of miliseconds it took to render the previous frame. But framerate counters like FRAPS will count the number of frames rendered in the last 1000ms, which makes it really hard to identify actual stutters because a loss of 2 frame will cause the counter to drop to 58 when a frametime counter will log a sudden drip to like 20 FPS for a split second. 

[Azakius]

Awesome. Thanks for the detailed responses! Much appreciated! 

[Nathanpete]

8 minutes ago, Azakius said:

Awesome. Thanks for the detailed responses! Much appreciated! 

Go ahead and marked as best answer pls so it isn't in the sidebar. 

Edited May 20, 2021 by Nathanpete
Ouch