Bitmain Antminer U3 keeps going Zombie 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.
This is a known and notable problem with Antminer U3s.  It's discussed at various locations around the Web.

The design couples the USB and miner +5V power rails, which is not good practice.  USB interfaces should be both electrically and optically isolated.  When a unit goes ZOMBIE, it generally requires unplugging and replugging to restart it, which fits with the above.  Some commenters claim that cutting the power lines in the USB cables improves reliability.

However, the maintainer of cgminer comes right out and says that the design is inherently unstable.  In light of my own experience I agree.  I ran three Jalapenos on a dedicated Pogoplug linux system for a year with no problems.  Two U3s have been on the same Pogoplug for two weeks now, and neither has run for 24 hours straight.  They're going back to the seller tomorrow.

Long and short of it, if you get a stable unit it will serve you well.  But most of them are unstable to at least some degree.