Random Drop in hashrate on certain cards

[opies32765]

Hi guys

Sorry if this has been asked before but cannot find an answer to this. I have several rigs with anywhere from 6-8 GPU's on them. GTX 1070's. I am using claymore miner. Every few seconds or so i will see the hashrate drop on certain cards then after a while they will go back up. I thought maybe a particular card does not overclock as well as the others but then a different card drops in hashrate on the same rig ?

Is this normal and has someone else also experienced this. Im thinking it might be a power issue(lack of) ?

Thanks in advance