NVIDIA's new RTX 5090 requires 4 x 8-pin connectors for its power (delivering 600W) when used with an adapter setup (rather than a new 12V-2x6 connector), but what about if you only have a 3 x 8-pin setup for whatever reason?
As VideoCardz points out, this might be because you're short on power connectors, or you just don't have quite a beefy enough PSU, but the interesting spin on the RTX 5090 here is that it works just fine on 3 x 8-pin connectors.
Obviously, this will only supply 450W, so the RTX 5090 will operate at a considerably lower level than its TDP. (Which is 575W, at least for the baseline graphics cards - that can go up to 600W with heavyweight third-party cards like the ASUS ROG Astral (pictured top of this article, though its power usage is nothing compared to the GPU's mind-blowing price tag).
With its testing, ComputerBase confirmed that a Zotac RTX 5090 - and also the mentioned ROG Astral behemoth - will work with 3 x 8-pin connectors, and what's more, these GPUs aren't that much slower.
As an average with 4K resolution benchmarks, the RTX 5090 running at 450W with the trio of connectors instead of four is only 5% slower than the fully unleashed GPU - not a massive amount of difference. And, of course, the graphics card is running at a much more comfortable level here, certainly compared to the full 600W.
If you were wondering if this behavior extends even further, to a scenario where just 2 x 8-pin connectors are employed, the answer is no.
Indeed, attempting to manually drop the RTX 5090 below 400W is a no-go, so it's not surprising that only a pair of connectors supplying just 300W is not feasible.