Interesting....
I have a gimpy R4 with 1 un-responsive board. Not sure if I ever swapped the controller ports to see if it is blown controller I/O or really a dead card. Will have to try that first.

If the 'dead' board shows up, well I just so happen to have a spare s9 control board from one relegated to being for spares. Some time I really should send the 3 dead hash boards (from different miners) off to MyRig in Colorado for repair/replacement...