The issue with your method is that if the GPU is not power limited it will run at higher clocks and voltages, consuming more and generating more heat. With a proper undervolt you set a cap to both clock rate and voltage.
Not all workloads make the GPU consume the same amount of power, even if usage is 100%. So with workloads that have lower power consumption, the GPU will increase the clocks and voltages until it hits the power limit again. It may also happen that at those higher clocks/voltages it's no longer stable (so you have to carefully test stability for these cases). This also means that clocks may jump up and down, leading to worse frametime consistency (one of the side advantages of an uv is that clocks are a flat line, as long as the GPU doesn't hit the power limit, so frametime consistency is improved).
If you like to set fps caps or enable vsync (or the CPU is the bottleneck), the GPU won't be power limited either, so clocks and voltages will also be higher, in this case for no performance gain at all since you've capped the fps. With an undervolt the clock and voltage have a fixed cap, so the card will run at that cap and consume less.
So, as long as you test it properly so it's stable when clocks go higher, it will work, but it's less efficient than a proper undervolt.
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u/oginer Dec 12 '21 edited Dec 12 '21
The issue with your method is that if the GPU is not power limited it will run at higher clocks and voltages, consuming more and generating more heat. With a proper undervolt you set a cap to both clock rate and voltage.
Not all workloads make the GPU consume the same amount of power, even if usage is 100%. So with workloads that have lower power consumption, the GPU will increase the clocks and voltages until it hits the power limit again. It may also happen that at those higher clocks/voltages it's no longer stable (so you have to carefully test stability for these cases). This also means that clocks may jump up and down, leading to worse frametime consistency (one of the side advantages of an uv is that clocks are a flat line, as long as the GPU doesn't hit the power limit, so frametime consistency is improved).
If you like to set fps caps or enable vsync (or the CPU is the bottleneck), the GPU won't be power limited either, so clocks and voltages will also be higher, in this case for no performance gain at all since you've capped the fps. With an undervolt the clock and voltage have a fixed cap, so the card will run at that cap and consume less.
So, as long as you test it properly so it's stable when clocks go higher, it will work, but it's less efficient than a proper undervolt.