Try 15.12 drivers on those cards, or 16.10.1 if you have to have newer for some reason. I've not tested 16.12.2 specifically but 16.12.1 was 5-10% slower on ALL of my testing vs the other 2 versions (16.9.2 was same speed as 16.10.1 but I prefer WQHL qualified versions when possible).
Roll Back to 16.11.3 Crimson. Total Result: 680 h/s is it limit ?
hI, I have the following problem: I have 3 video cards, two XFX R9 280X and one Sapphire R9 280X OC. I'm mining on ZEC. When I have all three video cards running on Clymore MIner, the result of two XFX R9 280X is 42 H/s & 43 H/s And the result of Sapphire R9 280X OC is 32 H/s (to be considered that this model is better than two others) When i'm running only Sapphire R9 280X OC - the result is about 45 H/s . What is the problem? Why does the speed decrease when running in parallel mode? How can I settle this?