Hi guys,

good news. It took me and my friends about a week to debug the 16-chip board but now it's nearly finished. To be brief: there were quite some bugs in the firmware. Also we've fixed some suboptimalities in the firmware operation. But now it's very reliable and predictable with bfgminer: you tell the board how fast should it operate the chips, and you get exactly that speed all the way between 500Mh/s per chip to 1700MH/s per chip. With the 16-chip board modifications to bfgminer were also necessary: at high speeds the board completes its work queue too quickly so that a significant amount of time was lost in idle.

With careful thermal design and at 1.025V power, we can run the 16-chip board at 27.2GH/s rated speed. bfgminer currently reports 26.3GH/s but it may change due to averaging.

I'm going to post the firmware updates shortly. A question: what is the optimal way of posting the firmware updates? I could send it to the author of the original project to be incorporated in the github repository. The bfgminer software also has to be modified for operation at maximum speed.

The Texas Instruments voltage converter is pretty overloaded at these speeds. Both inductors and FETs on it heat a lot despite forced air coolong. At least, small heatsinks must be mounted on them. Also I'd recommend making 10-chip boards or placing less than 16 chips on the 16-chip boards such as 12-14 in order not to overload the voltage converter.

http://s020.radikal.ru/i719/1401/62/b501996fcfa8.png