Just wanted to share my config and cpd:

1x Club3D Radeon R9 270 '14 series (146W)
XPMclient version 10.2.1
Catalyst driver 15.7.1
Windows 10 Pro N

platform = "amd";
onCrash = "0";
cpuload = "1";
target = "11";
sieveSize = "630";
weaveDepth = "40960";
width = "22";
windowSize = "4096";
devices =        ["1"];
sieveprimorial = ["13"];
sievePerRound = ["6"];

My CPD is 0.21