Is this true or is it just that the default configuration draws a crazy amount of power? I wouldn't imagine running a 5090 downvolted to 75W is useful, but also I would like to see someone test it against an actual 75W card. I've definitely read that you can get 70% of the performance for 50% of the power if you downvolt cards, and it would be interesting to see an analysis of what the sweet spot is for different cards.
If you're undervolting a GPU because it doesn't have a setting for "efficiency mode" in the driver, that's just kinda sad.
There may be times when you do want the performance over efficiency.
I can confirm you that downvolting can get you the same tier of performance (-10%, which by the way is 3 fps when you're making 3 and 10 when you're making 100, negligible) by cutting power consumption by a lot, how much is that a lot depends on the specific gpu. On the 4090 you can get 90% of the performance at half the power draw, lower tier car have smaller gain/benefits ratios.
I'm currently running a 150 watt GPU, and the 5070 has a 250 TDP. You are correct. I could get a 5070 and down volt it to work in 150ish range e.g. and get almost the same performance (at least not significantly different to notice in game).
But I think you're missing the wider point of my complain: it's been from Maxwell that Nvidia hasn't produced major updates on the power consumption side of their architecture.
Simply making bigger and denser chips on better nodes while keeping to increase the power draw and slapping DLSS4 is not really an evolution, it's laziness and milking the users.
On top of that: the performance benefits we're talking about are really using DLSS4, which is artificially limited to the latest gen. I don't expect raw performance of this gen to exceed a 20% bump to the previous one when DLSS is off.