I realized tonight I was using an old version of sph-sgminer (https://bitcointalk.org/index.php?topic=475795.0). I noticed this because the 280x on my main PC was running at 2.35MH while all my dedicated miners were running 2.1MH. Settings were the same, cards were the same, the only difference was the miner on my main PC was newer. Anyways all my 280Xs are now running @ 2.275 - 2.35MH thanks to using a newer version of this miner. For those who don't already know: Bitcointalk page for this miner - https://bitcointalk.org/index.php?topic=475795.0 Latest miner as of today (use the link above, I won't be updating this as newer ones are released) - https://mega.co.nz/#!eZhiCZbA!BDE1xMfi_6iE-PVzXxda5KtAmMbBY5tMGwXKm-sIgKY Settings for 280x - "-k darkcoin -I 18 -g 4 -w 128 --gpu-engine 1100 --gpu-memclock 1500". I can up the gpu-engine to 1150 on some of my cards and this does result in a small hash increase, try it and see if it's stable for you. Anyways just wanted to share since this was a very simple ~10% hash increase for me and maybe others are still mining with an older version like I was.