Ok, I benchmarked my Asus 3080 TUF OC in some orientations. Ran Furmark for about 10 minutes per orientation per test, which was enough for the temperature to stabilize. My case doesn't have any side panels yet so it's pretty much open air.
Here are the results with stock fan profile:
Orientation | Temperature | Fan speed | Fan RPM |
I/O on bottom | 67°C | 61% | 1320 RPM |
I/O on top | 76°C | 75% | 1960 RPM |
Horizontal, fans facing up | 68°C | 62% | 1360 RPM |
Next, I tried a fan speed normalized test to test if the heatpipe was really the bottleneck. If this were to be true, the I/O on top orientation would not become a whole lot hotter with a slower fan speed, no? Let's take a look:
Orientation | Temperature | Fan speed | Fan RPM |
I/O on bottom | 65°C | 65% | 1500 RPM |
I/O on top | 81°C | 65% | 1500 RPM |
But it does. And this makes the difference between both orientation painfully obvious.
So I think we can conclude that, with this heatsink design and this amount of power draw, heatsink orientation makes a lot of difference!