Hi all, I'm testing a switch for a ROACH2-based packetized FX correlator. I currently have a single ROACH with 8 SFP-ports connected, 4 on a 2m QSFP->4xSFP cable, and 4 on 3m QSFP->4xSFP cable. Both are passive copper (30 AWG). The switch is a Mellanox SX1012, which might be the root of the problem -- Jason, I'm about to email you :)
The shorter cable works great, but the longer cable is dropping a few percent of packets even at very low data rates. I'm still investigating, but it looks like sending down the long cable to the switch and receiving on the short cable seems to work better than the other way around. I have left all the implementation settings on the 10gig (v2) block at defaults. Does anyone have any advice on what pre-emph settings etc. might improve things? Thanks Jack
