If this helps anyone, here's the config file I use to get 6.8 MHS out of 3 280x GPUs:
.\sgminer -k darkcoin -o stratum+tcp://stratum.multipoolmining.com:5555 -u my wallet address -p x --lookup-gap 2 --thread-concurrency 8192 -g 2 -I 13 --auto-fan --gpu-fan 0-85 --temp-cutoff 90 --temp-overheat 85 --temp-target 70 --gpu-memclock 1500 --gpu-engine 1180 --gpu-powertune +1
I played with many configs to come up with this one.
I get the similar hash rate with 4 x 280x. But mine are Gigabyte and are notorious for hahsing less than other brands. I get 1.6 average each.
dude, check these settings
https://docs.zoho.com/sheet/published.do?rid=12cbm2fe8ce55abb2476daa0f8c576b442d40&mode=htmland maybe you should check your drivers too before making any changes.
i run a single gigabyte r9 290 at ~2.4 mh/s but i have it underclocked and undervolted and it pulls 120watts off the wall, i find it the best ratio for now
290 are more powerful. Your hashrate is normal. Pulling 120W from the wall is probably because you are mining with x11. Scrypt will double that.