You just helped me out man. :-) 🦊 I've got an RX 480 unit in my 16.04 Ubuntu installation and it wa Dog-slow with Claymore's Monero miner. That little -dmem 0 command made all the difference. Now I can use my workstation and mine at the same time. Many thank-you's. :-)
Congrats! Specifying -dmem 0 solved the exact same problem for me. I'm still trying to figure out how to make Claymore's CryptoNote Windows CPU Miner v4.0 work.