Board 3 was performing low when compared to the two another boards.
This was with the stock frequency 600 Mhz.
I changed the frequency to 550 Mhz, then let it run for a while and get warm.
Board 3 instantly performs better with the 550 Mhz than with the 600 Mhz.
Then after a while I change the frequency back to 600 Mhz and it runs okay.
Not exactly about 12.93Th/s like it should be but about 12.6Th/s and that is the best it can do.
Any frequency past 600 Mhz is a problem for the board 3.