Does anyone know which is the last good Polaris driver version before they destroyed performance when re-writing for the 5700XT?
Destroyed performance? I'm running 19.8.1 on all my rigs and my performance is uneffected, if anything they're more stable across 15 Polaris model cards, 580's, 570's, 8GB and 4GB....
Not sure where you're getting the hit.
As for the hanging on closing the miner mentioned above... I've seen that when under volting the cards, or trying to push the clock to high, however I do not experience hanging of the miner that often.
I have 4 of my own rigs, and have provided support on well over 25 others... and that ranges on memory through all memory types.
Very interesting you're experiencing it consistently.
19.4.3 runs fine for me but 19.8.1 runs about 8% lower hash. I know there was a 19.5.2 in there somewhere, not sure if it gets the same degradation. There was talk of lower gaming performance on Polaris with the newer Radeon drivers when Navi support was introduced. It was assumed that it would get worked out. I see the same on my rig using Claymore 14.7 in Win10 1903. Are you running under Windows? Also on mine, the strap and rxboost commands don't work. They say they work, but the values are unchanged and so is the hash rate. So I still have to run a modded BIOS with the straps burned in.