System gose down every time that happen .!? 1080 ti

hey guys i got 2x gtx 1080 ti and one 1080 … currently im using Nicehash legacy to mine multi Algorithm its doing well
untill i over clock my 2x msi 1080 ti duke
overclock setting
Power limit 85
Core clock +200
Memory Clock +550
Fan speed on 80 %

nicehash legacy change between algorithm to pick out most profit algorithm to mine its work well but when i over clock my 2x 1080 ti any nicehash miner cant mine Zecash equihash algorithm and prog can`t change between algorithm all system stop working and i have to Restart windows so i can mine

notice i used Ewbf miner to work Very well in mining zecash with overclock setting

any one knows why this trouble keep happing when i used any nicehash miner with overclock setting

I have noticed this as well. For me I think it was an instability issue that it thought I had but it could also be temperature. How hot are your cards running?

porblem solved

that`s happen with me coz of unstable Overclock setting