run this and monitor you temps and all when doing it
http://www.numberworld.org/y-cruncher/
Decimal Digits: 1,000,000,000
you got 16gb memory that's test option -0- benchmark pi then select benchmark option 1 then option 6 foir the Decimal Digits: 1,000,000,000
just don't exceed the test over your available memory it shows you have to use at the top .
that test will run your memory and cpu to its fullest
a old run of mine and got my cpu to 78c -74c all cores
Processor(s): Intel(R) Core(TM) i5-4670 CPU @ 3.40GHz
> Logical Cores: 4
> Physical Memory: 16,756,445,184 bytes ( 15.6 GiB )
> CPU Frequency: 3,398,990,144 Hz
> Program Version: 0.6.7 Build 9457 (Linux - x64 AVX2 ~ Airi)
> Constant: Pi
> Algorithm: Chudnovsky Formula
> Decimal Digits: 1,000,000,000
> Hexadecimal Digits: Disabled
> Threading Mode: 4 threads
> Computation Mode: Ram Only
> Working Memory: 4,859,459,952 bytes ( 4.52 GiB )
> Logical Disk Usage: 0 bytes ( 0 bytes )
> Start Date: Wed Feb 25 03:01:59 2015
> End Date: Wed Feb 25 03:05:01 2015
> Computation Time: 174.334 seconds
> Total Time: 182.220 seconds
> CPU Utilization: 385.460 %
> Multi-core Efficiency: 96.365 %
http://www.numberworld.org/y-cruncher/benchmarks/charts/1b.html
after that ust the highest pi run [should be run option 7 ] that uses most all your 16gb to do
maybe test the hard drives and there data cables ??
like I say unless you can test your card like in another compurte to see if its as bad or work well in it ? I seen quite a few guys needing to rma there skylakes back to intel ???
with out some kind of process of elimination all you can do is sit there and guess at things and hope you stumble on to it or the cause ?
just googling overwatch gtx 1070 frame drops seems a lot on that [plenty] seems that game is known to do this ?
https://forums.geforce.com/default/topic/940424/fps-drops-and-stutters-on-overwatch-/?offset=5
maybe be them games behavior ??