disq wrote:How does one determine the effectiveness of an in-game FPS limiter? How do we know if it's a good one, better than RTSS?
It's not always straightforward. That said, there are some ways to tell...
First off, a lot of modern games share engines. Typically, to the best of my knowledge, engines such as UE3, UE4 (which many modern games currently make use of), Frostbite, Overwatch, and Source (Apex Legends being one of them) have in-game FPS limiters that have lower input lag than RTSS. At worst, while I haven't come across this, some in-game limiters may have the same
input lag as RTSS.
As for frametime peformance, unless you're seeing
the difference between the RTSS and in-game FPS limiter with your own eyes where stutter, frametime spikes, or general frame pacing is concern, ignore the graph; RTSS can read an in-game limiter above and below the set FPS limit, but when you're limiting FPS with RTSS, it can't read anything above it's own set limit, which is why the graph looks perfectly flat when your framerate is sustained above it.
In reality, RTSS fluctuates as well (around 1 frame drift), just not as much as in-game limiters (anywhere from 1-3 frame drift, typically).
Lastly, some FPS limiters (like Source) will sometimes (depending on the game) report a lower/higher FPS than the limit you have set. For instance, during my original tests, I set CS:GO's limiter to 142, and it hovered around the 138-139 mark.
In that case, it's fine (better for it to hover slightly lower than your set limit as opposed to higher), but, for in-game limiters, you want to make sure the reported limit matches the set limit, even if that means raising or lowering it slightly past your intended number (though I'd say this behavior is rare as well).
Otherwise, unless the in-game limiter in question is particularly unstable/unreliable (the only recent in-game limiter I can think of is the one featured in the modern CoD titles), then G-SYNC will take care of smoothing out any frametime inconsistencies the in-game limiter introduces over RTSS, all the while giving you lower input lag levels.
All told though, if you don't want to be bothered by any of this and aren't sure about the in-game limiter in question (barring the aforementioned UE4, Frostbite, Overwatch, and Source engines), RTSS is always better than an uncapped framerate (even without syncing, so long as it is the framerate's limiting factor), is basically neutral input lag-wise (good in-game limiter effectively create a negative reduction in input lag), has excellent frametime performance, and can be used consistently in the majority of games without worry.