I have 8 RX 580s, 6 of them ASUS RX 580 8GB and 2 of them XFX GTS Black Core Edition RX 580 8GB.

In GPU-Z, my ASUS cards' ASIC quality ranges from 69 - 76%, while both my XFX are >76%. My two lowest ASIC quality ASUS cards, 69% and 70.2%, require 25 more mV more at 1100 core clock while mining (825 mV). All the other cards are stable at 800 mV, including XFX cards which are clocked higher at 1175 core. There seems to be some correlation between ASIC quality and undervolting voltage, but at the moment, with such a small sample size, it is just anecdotal evidence.

How about you guys?