Fluctuating Hashrates and GPU Usage Mining Ethereum - help!

[Enigma54]

I've encountered this strange issue in the past few months where my hashrates mining ethereum will intermittently drop from about 30 Mh/s to 20 Mh/s. Everything was stable at around 30 Mh/s before this and I don't know what has changed to have caused this. When I look at my GPU usage in MSI Afterburner, I can see that there are frequent dips instead of a constant 100% usage.  Is this a power supply issue? I'm using a Seasonic 1250W Gold power supply and that's powering 6 GTX 1070's and 2 GTX 1060's.  I set the Power Limit to 60% in Afterburner for all 8 cards and my smart plug is measuring about 900W of consumption.  I'm using overlock settings of -100 on the core clock and +650 on the memory clock in Afterburner, but I've since reset both overclock settings to 0 just to see if that would solve the issue - it does not.

I'm using Windows 10 and Claymore.  I've never seen this issue until about a few months ago and I wonder if the Byzantium update affected things?  The other weird thing is that if I switch my rig to mining Zcash, I don't have this problem at all and the GPU usage when mining Zcash is at a constant 100%.  So the issue only seems to happen with ethereum.  I have a second PC that only has two 1070's, and this issue does not surface so I'm really puzzled. That's why I'm thinking maybe it's the power supply?

Can anyone help?

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[bouldou]

I think it may be linked to a PSU problem

I've had similar issue for my rig, and I've bought a 550W PSU + Add2PSU adaptor, and it's much more stable now

It's quite cheap, you should try : buy a PSU online, and if the problem is still here, send it back 

[Enigma54]

I think it may be linked to a PSU problem

I've had similar issue for my rig, and I've bought a 550W PSU + Add2PSU adaptor, and it's much more stable now

It's quite cheap, you should try : buy a PSU online, and if the problem is still here, send it back 

That's my suspicion as well, but when I switch to mining Zcash, this problem does not come up and the power consumption when mining Zcash is about the same as when mining ethereum.  So if it's the power supply, why is it only specific to ethereum mining?

[hardaccount]

I have the opposite problem. Mining Zcash the GPU Usage Fluctuates, but mining ETH it stays constant. Any suggestions are appreciated.

[mahof]

same problem here with rx570s i have changed the power but coulnd not solve on an other rig with rx470s no problem w10 and claymore, eth hashrate is 29 in one second  goes to 20 after a few hashes goes up to 29 maybe a driver problem i think because core clock goes to 800 and then up to 1100 but could not solve yet