Mine was working fine at 662 for 36 hours, then one of the board went to zero... I have to lower to 650. So maybe then run fine only at 500M finally...

I also strongly disagree with such marketing practices. They made sure the first batch would be perfect so all the reviewers would make free publicity for them about a 750M stable Z9mini then the orders should have flow in from people expecting the Z9 mini to all be like the ones they saw in the reviews. Also the first batch came in with new promises of transparency from Bitmain with the published log of each unit shipping but for batch 2 it'S radio silence again.