270 card 820/1250:
  new miner   < 3.2 cpd
 9.4.1 < 4.8 cpd

7850 820/1250:
 new miner <2.5 cpd
9.4.1 <3.7

difference 50%

for 9.4.1 driver 15.7.1 with ocl 14.6
for  the new miner work only witout ocl driver in miner (15.7.1)