You know, the funny thing is ... your temp doesn't drop.  It looks like the card is doing the same work but is being miscounted for some reason.  When mine slows, I usually see a couple of degrees drop off of the temp.

To be honest, if I sit and watch it for a bit I can sometimes see it drop the rate while I watch.  I suspect it has a thread or two dying inside and isn't able to relaunch them.  If yours is always after you walk away,  I would head straight into the Control Panel and check to see if you have some power saving mode selected after some period of inactivity.

My guess is, that this is related to GPU's power levels. I use GTX 970 on Ubuntu 16.04 and it has four power levels 0..3. When I'm mining, it spontaneously goes to level 2, but I can force it to level 3, and it gives slightly better hashrate with it.

Check GPU's power level, if it changes as your hashrate changes.

Hi,
I am Mining Ethereum and Decred (or just Ethereum) with ethermine (and suprnova for Decred).
I have a GTX 1070 (only one, it is my first try on this) in my gaming computer. So I downloaded claymore and followed a few tutorials and explanations about configuring my miner.
I have a good 27.7 Hashrate with stock settings and after OC and some tweaks I have reached 30.5 Hashrate in solo mining.
I am using Windows 8.1 Pro.

My problem is that, for example with the stock settings, my 27.7 hashrate only stays if I am somehow using the computer at the same time that I am mining. If I let it mining alone, closing every other program, etc, my Hashrate drops, in 3 or 4 minutes, to 18. And this happens always, after I have been AFK.
After that, the miner remains in 17~19 for hours, being consistent and stable, but at 18 and not at my 27 peaks.
But, if I stays using the computer, the miner remains in 27~28 being consistent and stable.

Do anyone have any clue about what can be happening ?
I already tried tweaking power options and can't make it change a bit. It is still the same (may be it is still the power options and I lacked on changing the proper setting, i don't know).

Thanks a lot. I am pretty knew on mining.