Yo,
I have a Sapphire R9 390 Nitro. At stock speeds (1040mhz) it boosts properly under graphic loads. However, applying even a 1mhz overclock in MSI Afterburner causes the card to be locked at idle clock speeds (300mhz) under load. I've tweaked countless settings, used DDU to wipe drivers and installed the latest from AMD and still no change. Any suggestions?