i just recived my 2nd batch. mine too. 3rd chain die at 681 or up.
What hash rate are you getting at 681 or close. Do you get hw errors on any chains or does it just hash at 0 when you go at or over 681
same here... what about flashing the may 2018 firmware on to it?.... my batch 1 runs fine at 750..17 sols batch 2 one board dies above 675 freq.. 14 sols...
I'm wondering if bitmain hasn't cherry picked hashboards for the Z9s over the minis in this batch?
In theory I'll have a Z9 next week to see how (if?) it overclocks.
I wouldn't imagine their yield suddenly going down across the board on OC stability.