Thanks for the search links, I could fix the nodeboard which is now enabled, after replacing the compression connector and doing the usual clearallogs... commands in pod then resetenv enableall... in PROM menu.
But the shoebox is still down despite those commands repeated several times and reset cycles. I know its XIO connector is good because
-I cleaned the midplane pads
-a shoehorn in the same slot is detected
-I replaced the compression connector
-there are no warning messages in console like those from IO6 before reseating it
Only its PROM is detected in hinv (from IRIX, not PROM)
IO6prom on Global Master Baseio in Module 1/Slot io2: Revision 6.156
The flash was successful: before, tail of hinv was
IO6prom on Global Master Baseio in Module 1/Slot io1: Revision 6.80
No one else knows of io2 slot
io1 io4 io5 n1 n2
What to check next ? I did not find detailed help for POD command dgpci and its options, it is not in man prom.