Frames go down before usage goes up, why?

Ozz · March 30, 2022

So I have a Ryzen 5700G and an RX 5700XT with 32G of ram clocked at 3200. My monitor only has 75hz refresh rate, so I target that and use vsync.

My problem is I see my frames dropping down to 50 or less, but my cpu and gpu usage isn't going up. It just stays around 60% or so. Why is my usage not going up to keep the framerates up?

Is this a weird AMD setting I need to find and change?

Eigenvektor · March 30, 2022

36 minutes ago, Ozz said:

Why is my usage not going up to keep the framerates up?

Not really how that works. In general the CPU and GPU are working as fast as they can. They don't know anything about the monitor's refresh rate and don't do anything specific to try to match it. Their usage may be limited e.g. by memory speed or latency. The GPU can only work at 100% performance when the CPU can provide data to work on fast enough. The CPU can only run at 100% when the data it needs can be read from RAM or the disk fast enough.

Games with a target frame rate may dynamically adjust resolution or detail level if the engine can't meet the target frame rate, which might increase usage, but that depends on how good that mechanism is implemented in that particular engine. That's not a hardware feature.

(Oversimplifying a bit) 75 Hz means your monitor displays a new image every 13.3 milliseconds. VSync means your GPU gets locked/limited to that refresh rate. If it manages to produce a frame in 10 ms, it can essentially stay idle for the remaining 3.3ms before it needs to render the next frame, reducing its usage. If it takes 14 ms instead, it has missed a window to update the screen, so it'll essential be idle for 12.6 ms until the next opportunity to update the screen comes around. That'll lower usage a lot, but also means if your GPU isn't fast enough to meet/exceed 75 Hz, it'll actually drop down to half that (or 1/3, 1/4 and so on). Some engines dynamically disable VSync if the refresh rate can't be met to combat that. You could try disabling VSync, see what that does to your frame rate.