Can you get any sense of whether the packets are being received by the switch and dropped by the roach vs not being received by the switch in the first place? Can you change any transmission parameters on the switch?
FWIW, I think you can set preemph and other such params on the ROACH at runtime via software. Dave On Jul 22, 2014, at 11:27 AM, Jack Hickish wrote: > 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 >
