I have read folks theorize that the consumer playing cards have less mature firmware that winds up tripping the PCIe DMA protections on POWER9 that don't exist on x86. Not less than anecdotally this looks accurate, given that that same RX 580 is effective just wonderful within an x86 machine. https://amdradeonprow5700vs5700xt82603.activablog.com/14288290/the-basic-principles-of-12gpu-with-2-power-supply-rig-kit