RIG with 6 x R9 390
with -i 2 45 hs per card
with -i 0 95 hs per card
my 3x390 rig is same, guess it just silly processor. i have athlon x2 340 there and it uder 100% load with i=2. my other rig with similar processor but 4x480 is under 95-100% load but hasrate is better with i=2 there than with i=0