Right but I did not state the core voltage was 120V. The stated power consumption of an Avalon is 620w @ 120v which is what I used in my estimate. If each chip does indeed use 1.5A each then an Avalon would use more than 43kW so that can't be right. If the core voltage is 1.2V then each chip uses ~24mW by my estimates.
Power consumption = amps * volts. Avalon's power consumption at the wall, through the PSU, is ~620w @ 120v, so 5.16 amps @ 120v. The PSU converts that down to +12vdc to feed each of the three modules, figuring ~80% efficiency let's just call that 500w of +12vdc. This is 41.6 amps of +12vdc. Now each module has groups of chips fed by a +12vdc to +1.2vdc converter to feed the cores. ~500w @ +12vdc divided by 240 chips = ~2w per chip BEFORE the losses of the +12vdc to +1.2vdc converter. Those are usually incredibly efficient, let's call it 95%, so 475w of +1.2vdc, 395 amps.
I'm sure I'm butchering all the math here with calculating PSU efficiencies and such but this shows 1.979 watts @ +1.2vdc or 1.64 amps per chip.
I hope this makes sense to you. With these numbers, 3 of their chips, which provides (63,000/240)*3=786MH/s could be powered by a USB port providing 0.5 amps @ +12vdc. Call it 2 chips to give a nice buffer under the 0.5 amp limit and you have a neat little device. It won't generate crap for BTC though.. better off targeting something in the 5-10 GH/s range.
Thanks! Been meaning to get around to figuring out the math on this.
I'll make the PCB with room for 3 chips (the third one can be optional). Either you can run the two chips to the max or settle for running all three at slightly slower speed, but with more overall hashing speed. Using 3 and running them slower might be a good option for passive cooling too (decided to go with passive cooling).
You are right, this does not produce crap for the serious miner. But IMO the project will do few things:
1) Help the new curious miner get into bitcoin at a very low cost yet still be somewhat competitive compared to the GPU or CPU.
2) It would be cheap enough and small enough that they could be given out to friends to get them "hooked" on the concept.
3) Set the ground work for a better atmosphere with regards to ASIC competition; make cheaper mining options quickly available to anyone.