It's pretty simple why you'll see a Turing GPU do what you described:
The game's normal pre-render > render pipeline (raster pipeline, or final output to a display) is waiting on results from the RT cores (and/or maybe Tensor cores if DLSS is involved). It's generally always the RT cores as they are expensive and relatively few for what we are asking of them and are doing calculations that make anything before them look so very simple.
The problem is basically the result of a bottleneck within the GPU's own architecture such that using RT is very much capable of becoming a bottleneck in terms of raw latency...
Very interesting, and that makes sense to me. Like I've said before, new tech...methodologies are not yet fully implemented...it will take time to figure out how to optimize both the hardware and the software.
So, if I'm getting what you're saying, it's not that all those GPU cores are actually "working"...it's that they're being sort held in "reserve" so that they can process their data when the time arrives? Kind of like saying, "I can't do anything else for you -- I'm waiting here on-call." They're not drawing voltage...but they're "in use". Ja? Kinda?
Just a note / clarification: from what I've heard, at least, it's actually fairly normal for a GPU to run at 100% or close to it in gaming, especially if there's no limit on frame rate. If it's running 100% when idle then there is a problem.
If GPU isn't hitting or approaching 100% with a maxed out game that is not so old it can't use all the GPU's capabilities, my understanding of it is that that indicates a bottleneck elsewhere in the system.
In general, across all of engineering, not just with PC technology, you do not ever want anything running at 100% constantly (idle
or in operation). A GPU processor degrades based on the amount of sustained voltage moving through its architecture. Just like any electrical engine, when you put a lot of voltage through something, it generates a lot of heat. All materials expand when heated, and contract when cooled. If that change is too drastic or too strong, stress and eventually damage occurs. The reason GPUs and CPUs "throttle" when they hit a certain temperature is because, if you continue heating it up beyond that point, you will literally fry the part, causing physical damage. So, if we're right at the threshold of what a processor die can do, and we leave it sitting there for long periods of time, we're eventually going to fry it anyway. Think of it as buying a new car, and driving everywhere at 120-150 mph with the pedal all the way to the floor. Yes, it will be faster, but you're going to brick that engine before too long. Versus driving at 60-70 mph, and the engine will last for 10 years without any real worry. Or, in short, "Just because I can, it doesn't mean I should."
Power-User mentality, which is super-popular nowadays with all the overclocking, extra cooling, and massive benchmark scores is both super-flashy, super-fun...and super
expensive. It gets lots and lots and lots of attention...because it makes the manufacturers lots and lots of
money. But it's flashy in the same way that race-car driving and parkour is. The end result is: it's risky. If you push a system like that on a regular basis, you
will burn through your hardware faster. In my own experience, I've burned systems out completely and had to replace parts within 1-2 years in most cases. (I imagine 3 years would be more the norm nowadays, with more robust parts, liquid cooling, streamlined airflow in cases, etc.) This is fine if people enjoy it and have the money to burn! But it will burn.
My big encouragement for people to
avoid Power-Use is for longevity, stability, and...the fact that if I sit them down at a system that is not overclocked and running only at 60 FPS, there's often no discernable difference between that and a system that's running at 120 FPS and cooking its hardware to death every time it's on. For example, I run TW3 at a locked 48 FPS frame cap, and I've had numerous people ask me how in the world I get it run so smoothly. It's the perfect indication that "brute force" is very often not the most efficient and effective way to manage technology.
TL; DR:
Trying to get my PC running at 100% constantly is simply never a good idea. Not when idle, definitely, but also not while in use. The actual goal for silky performance is to get it running smoothly well
below capacity, leaving plenty of overhead in case it needs to put the pedal down a bit to keep a steady speed while heading along an uphill stretch of road. It's that ability to power through intense moments on demand that creates the sense of smoothness. It's when a computer is forced to slow down that we feel like the performance is choppy, regardless of speed. Thus, if I drop from 60 to 55 FPS...there's no sense of change. If drop from 120 down to 55, I'll definitely feel it. So keeping it at 60 is how I make it feel "silky smooth". And the need for pushing the hardware to its limits...vanishes.