I got 2 U3 running on Linux Ubuntu cgminer 4.9.0.
Dedicated Power Supply
New short USB cables
Cold room ambient 5 degrees celcius (heat sinks don't go over 40 degrees)
Not once have I managed to run them longer than 24 hours. Does anybody know why they keep going ZOMBIE?
Once they go ZOMBIE like this they are not detected by cgminer and sometimes show in lsusb but not always. The only way to fix this is to remove USB cable and Power, restart cgminer, then plug power back in and USB.