tried all old and new versions of miner and still the same. My CPU is used only uder 30% with 8 threads...
can you help me please?
Thanks!
That is very odd! It is using only about one quarter of the available CPU time when it ought to saturate all cores. The hashrate is only about one fifth of what I would expect to get with that CPU. Is the CPU time used by minerd.exe spread across all cores, or restricted to just, say, two cores? If the minerd.exe process was restricted to just two cores, that might explain your results.
Even the older minerd would generate (I expect) around 30 Kh/s.
You are not using my XMG Miner Speed Controller are you, by any chance?
I know that some anti-virus software can interfere and slow things down, but not usually by such a large amount. It would be worth a try switching any anti-virus software off and re-testing.
EDIT: As an afterthought ... try adding --quiet to the minerd.exe startup command line.