with my settings on the page back, with volts at 830; and the old cgminer (yes, its what works, and I dont want to go through the rigamarole to compile in windows; yes lazy)...
I am seeing A:54000 R:0 HW:5
Thats an ok HW rate to me (about 1 hour uptime). It normally wants a replug once every other day. sometimes goes a week without touching it.
This is on a 2.5A power supply that it shipped with.
The average hashrate is 62.24GH right now.
I have the diff set at 1K because it mines to a solo account.
The math as far as power consumption and settings doesnt make sense.... It defies logic. it should be having trouble doing its job; that's for sure. I wonder what my oscilloscope will show me once I finally bring it home.
aside from thinking the harmonics of the power draw keeping the device charged with just enough juice to stay stable.... its a strange thought.
I do have a little bit of active cooling on it, but presently, its minimal. I also replaced the thermal grease with dialectic grease last time I took it apart to clean it.
One thing I would suggest is to keep an eye on the power brick that they came with. There has been a few post's about them melting!
If you use the normal common settings you should have no worry about melting power supplies. Its when you overclock you run into problems. I have had my 3 U3's running for 4 months now and my only worry is the power supply is cold, which means it's silently zombied and isn't hashing.
I would be very curious to see a scope of the power consumption circuit. I am still using the default bricks that came with the unit as nothing I've heard suggested they are more stable with a better supply, and a 25A PSU isn't cheap. I thought of going the route of the computer supply and using the PCIe power connections but again, I haven't seen anyone here confirm that its more stable.
Earlier someone posted in this thread about the usb and power circuits being shared and I can validate this somewhat as I can run the U3's without the 12v connection but they don't mine, I assume the usb port is not sufficient to power it up properly and when the unit silently zombies I suspect the usb port is getting flaky power. Resetting it and the port starts communicating again.
I've tried software based resets but this does not seem to work. I've tried shutting off the miners but as long as they stay connected via USB, they won't recover until that usb cable is pulled and plugged back in.
Perhaps a smart robot who can watch these all day is the solution