There has been a request to discuss over clocking these boards. I'm the designer of the board, and these are my thoughts on over clocking, but of course your results will vary and you could end up destroying your boards! I don't recommend doing any over clocking, but since Bitcoin is about experimentation, here goes nothing!
These boards were designed to run at 4GH/s with ambient cooling on the heat sink. This allows them to run at <500mA and thus be USB2 compatible. When over clocking a Bitfury based design, heat is your enemy, you will need active cooling from a fan if you over clock these boards.
With the way Bitfury chips are designed, heat really is the enemy. As the chips heat up, they slow down and also start producing hardware errors. Software over clocking will increase the heat dissipated by the chip and thus can actually produce worse results. Same with increasing the core voltage. Software over clocking:
The current cgminer release supports software over clocking with the --bxm-bits=XX command line parameter. Non-over clocked optimal is 53 or 54. However, you can go to 55 or 56 if you introduce active cooling.Increasing the core voltage:
In order to get the Bitfury chips to run stably at higher clock values increasing the core voltage is necessary. Again, the boards were designed to get to 4GH/s so the core voltage was chosen accordingly. Increasing the core voltage will really increase the heat output. Cooling the boards with a fan is absolutely necessary.
The core voltage is set by three resistors, but the only one you want to change is R6. It is right in the middle of this picture:
As built R6 = 499 ohm, to increase the core voltage use a larger value, but don't go above about 1.5k. You'll need a 0805 surface mount resistor. To measure the core voltage the chips are seeing, measure across the decoupling capacitors that surround the Bitfury chips. Explaining how to desolder/solder a resistor is way beyond the scope of the forum ;-)Active cooling
I thought it might be fun to add a 40mm fan to the heatsink:
To do so, find a 40mm fan and screw it to the heat sink. Then solder the wires to the USB connector as indicated above.
Anyways, have fun hacking up my creation!