Passively Cooling A Radeon RX 480 Polaris GPU
Unfortunately due to the size of the backplate, it was hitting the DDR4 DIMMs on the test system being used. As a result, it wouldn't work in the top-most PCI Express x16 slot but had to use it in an alternate PCI-E x16 slot to have the clearance for installation.
The other unfortunate part was when the Accelero S3 was installed on the Radeon RX 480, it was a hair too high for fitting within the 4U height requirements. As a result, it won't work out in my 4U enclosures with their lid on.
For those curious about the thermal performance, I ran some benchmarks of the RX 480 with the Accelero S3 under different workloads on Linux while the Phoronix Test Suite was monitoring the GPU temperature.
Here is a look at the GPU temperature of the RX 480 with S3 cooler when the system was freshly booted and idling / basic desktop tasks for 15 minutes. Basically the GPU temperature was stable around 34C.
Next were a variety of 2D/desktop-focused graphics tests... The average temperature here was 44C but a peak of 76C, still not bad for passive cooling a higher-end desktop GPU. All the 2D test details and more via this OpenBenchmarking.org result file.