Strange issue with my RX 570s. They've been happily mining for some years now on Claymore. With OC I get a bit over 30MH/s so 18x in total. This has been super stable.
But Claymore is broken, so I switched to Phoenix 5.5c. It's working ok, but after a little while, one of the RX 570s will adjust the cclock from 1150 to around 900 MHz. This card has the lowest error rate, and doesn't get warmer than any other cards.
I've tried setting the cclock to 1150 for all cards, but that doesn't help.
The cards are overclocked through OverdriveNTool. If I restart Phoenix, all cards mines at the corrects speeds again for a while. It's always the same card that is the problem.
Is there any way to turn off this (watchdog?) autotune GPU Core feature?