[ofa-general] CX4 Optical Cables

[Charles Taylor]

Operational Question....

We have some storage nodes across the room from our IB switch and  
reach them with 10M copper cables.    These 10M cables have been an  
ongoing issue for us as they fail (start showing symbol errors) fairly  
frequently.    We  decided to start replacing them with fiber (optics  
imbedded in CX4 connectors) cables.   We got a couple of "intel- 
connect" 20m cables (note that I think Intel sold the business to  
EMCore).

When we installed the first cable yesterday we were surprised to see  
that we could not get link status on the connection.    The HCA in the  
host is a Cisco/TopSpin "LionCub" (board id=MT_00A0000001).

We have some newer (by one year) Mellanox branded HCAs on some other  
nodes (MHEA28-1TC, Lion cub, board id=MT_02F0110001).    When we ran  
the optical cable from the same switch port to the mellanox HCAs, we  
got link status and a LID was issued - no problem.

We are just wondering if anyone knows what changed between these two  
card/chip versions such that the optical connectors work transparently  
with the the mellanox cards but not at all with the TopSpin/Cisco cards.

Thanks,

Charlie Taylor
UF HPC Center