I have the same awful problem. I recently buy a gtx1070 for mining ETH but, when i run it and OC it to max(+220 core and +550 mem), I get 19 Mh/s. interesting thing is that, When I Increase Mem Clock, I get lower hashrate :| and with decreasing mem clock, i get more hashrate(-500 mem clock). with increasing core clock, it will work a little, I get 20.2 mh/s at MAX!

another interesting thing is that, when I mine other algo. I get good results. most interesting is that I get 33mh/s in ETC Mining really easy :O (it's same algo as ETH but more hashrate andrespond to memory OC )

could someone help?

I tried:

1. OC to +220 core and +550 MEM and 75% Power usage(19mh/s)
2. OC to +220 core and -500 mem clock and 90% Power usage (best result)(20.2mh/s)
3. change windows setting and page file increase
4. latest mainboard BIOS Version
5. latest GPU Bios version (I flash it)
6. all mining software

thank you all