Ok, found the prob. Problem was in activated overdrive by default somehow. Still, its pretty good results with it - max temp 68C with 310 mhashes/s. And I even not yet underclocked mem/undervolted it. Sweet.
What OS, Driver, SDK, Miner.... and clocks ?I can get 310+ MH/s from my Diamond Reference 6870's, but have to run them at 975 Mhs on the GPU clock to accomplish it.
(
Win7 x64, CAT 12.1, SDK 2.4, CGMiner 2.3.1, 975 Mhz GPU, 875 Mhs MEM, Stock Voltage)
Win7 x64, CAT 12.1, SDK 2.4, phoenix 1.7.4, 960 mhz, sapphire.