There has apparently been a rather widespread problem with the switch over from Samsung to Micron memory (GDDR5 not the GDDR5X used on 1080s). Seemed to be a power state prob with the Micron. This is supposed to address that issue....luckily, my 2 1070s are both of the Sammie persuasion and I've not dealt with the instability nor checkerboard schtuffs
Probably it's the same as some brands made in the past. While switching between IC they did not change BIOS and were issues with stability or overclocking just because of differences in timings.
Usually it's like first cards are on the best IC, then all are looking for something cheaper. We could see that all Nvidia cards at least since GTX600 series were starting with Samsung, then Hynix and at the end Elpida/Micron. General specs are the same but there are some differences in timings. All GTX1070 and RX400 started with Samsung IC but it's time to move to something else so we get Micron ( which is the owner of old Elpida ).