They've implemented a power cycle for GPU's under heavy load when thermals/power get too high:
https://www.phoronix.com/scan.php?pa...-Cycle-Scaling
Sounds like a massive hack to compensate for silicon that's getting pushed too hard. Supports the idea that big navi is unreliable for heavy compute in its current state, maybe with DCS enabled it could reliably be used albeit with a lower throughput.