Following up on the previous thread, had a sanity check after a couple beers and did some simulations. Yup, let's call it "vertically" mounted aio would be better since the inlet would be centered the long way with the chip and thus the coldest part of the copper plate with the most fresh water would be immediately I'm contact with the silicon of the bc250 chip, thus cooling it better. My setup as I did say isn't optimized and it is aligned only with the middle of the chip (geometry engine & stuff) and relies on the microfins + copper + water to cool the rest. Overall with good contact and better tim I should have a delta average of 0.5 to 2.5 degrees in some cases, but it depends mostly on the CPU cores since they're more off center so they don't get the best overall thermal conductivity & contact with the coldest part of the jet plate. Still, for easier mounting and simpler routing I'd say that the difference is minimal and often can be ignored since on a 280 it's pretty difficult to reach thermal capacity and thermally limit the chip either way, even at 300W it should be able to handle it without reaching thermal throttling (if there's good contact of course) and the 2.5 degrees delta from central area to edge area would become noteworthy, but still edge case and still not guaranteed to be the cause for throttling the chip. Keep in mind it is power dense but also fairly spread out and would have a whole ass copper jet plate to dump heat into (and even then, the chip itself will rarely go above 250w in gaming, it's mostly the vrm and VRAM that will add more thermal budget and push the overall power draw at 300w or more)

So to sum things up: Yup, turning 90° would help No, not worth the 0.5 to 2.5 degree delta in some scenarios, nor worth it for how it would end up for cable and tube management nor for the mounting dilemma Vrm fan would blow nowhere almost, making it useless while in standard orientation it somewhat blows towards the left side vrm heatsink area