Cool Thank you for your detailed answer, your experience is appreciated, I have 15 now running at 662Mhz to 668Mhz at 14,150Th 14,300Th with lessthan 10 HW faults and 00000% DiffA# they seem to be running better on the 650 fixed firmware then the Nov 17 Auto Fq Firmware.. and temps are 82 max.
Cheers
Jase
Based on my experiences with Antminer D3, some boards works better at higher frequency at the same voltage level. The correct frequency was only one unique frequency. Lower didn't work and higher didn't work also. It is probably because of chained chips are dividing voltage between each chip group a bit different at each frequency.
Check kernel log for "setting working voltage" where you will see which working voltage it applies with autofreq or with fixed voltage. Autofreq boards has different voltage for each board while fixed freq sets the same voltage for all boards. I was shocked, that at 600MHz fixed firmware applied 9.3V for the chain and at 650MHz it undervolted to 8.8V.