CSP Framerate Limit versus VSync and how not to cook a GPU

Helmut Skrdla · May 14, 2020

Hi,

I'm not sure if my assumptions are true, or if they have been discussed (search didn't turn up any stuff). Maybe this can either serve as a kind of PSA or Reality check to my logic.

I've noticed that even though I've been conservative with my CSP settings (i.e. scaled to accomodate a race start/full grid at a steady 60FPS and not thrown every nice thing into it at once), even when I'm running my car along, on a "simple" track, I've had constant max GFX temperatures. Even though I know my card could push more frames than my screen can render.

Normally that's one benefit I get from vsync at my 4K 60hz - it not only keeps the framerates smooth, it offloads the GPU during less intense scenes and allows some cooling.

But I assume that some parts of CSP, even though the visual image is framerate synced, might run faster than 60Hz beneath everything. Meaning - even looking freecam at a blank texture, which normally drops GFX loads dramatically, causes 99% load on my card.

So, what seems to fix it is the framerate limiter built into AC. Setting that to 60 while keeping vsync drops GPU load a lot.

Does this sound logical, anyone else noticed such behaviour?

Deleted member 197115 · May 14, 2020

Interesting finding, worth to test. Thanks.

Sascha Guenther · May 14, 2020

Recently I´ve read that you should not activate VSYNC with framerate limiter enabled as well since both options are equals to each other meaning if you have VSYNC ON let framerate limiter be OFF.

Helmut Skrdla · May 14, 2020

With my testing, I don't see any adverse effect on vsync by using a frame limiter of 61.

What I can really confirm now after further testing is that since adding CSP (which I did only this week, so I'm new here) my GPU was running constant 99% load whenver ACS.EXE was active. Even if minimized, even if the actual scene on screen was purposely "looking at the ground" simple, which in any other game relaxes immediatly the GPU load.

By adding a framerate limiter of 61, the card is showing much more varied loads between 75% and 99%, depending on which part of the track, other cars etc.

Maybe CSP could have it's own framerate limiter/internal frequency adjustment (if it hasn't already, but at least I can't find anything like that in CM).

Deleted member 197115 · May 14, 2020

Do you enable VSync in game or video driver?
Tecnically VSync acts as a frame cap, dropping frames excedding monitor refresh rate before they reach GPU.
Is your monitor 60hz?

Deleted member 197115 · May 14, 2020

Only tested in VR, two consecutive runs one with no limiter another with frame cap at 90. HMD driver always sync on 90Hz. Will try pancake next

Deleted member 197115 · May 14, 2020

And flat screen results

Keep in mind that during benchmarking in game VSync gets disabled so you need to force it in driver. May be this is what confused you.

Helmut Skrdla · May 15, 2020

I have VSync enabled via the game itself, and wasn't doing a benchmark, just had the AI Driver race around the same track from the same starting conditions. Definitley without the framerate limiter I see a different, very even GPU load (I don't have a GPU charting tool handy, like your excellent comparison shows).

Thanks for making the effort to check my assumptions... obviously there is some thing about drivers or settings that make a difference and it is not likely a general problem.