Hey Dave, Judging by the switch diagnostics, everything is making it through the switch and only being dropped at the ROACH RX end. I'm digging through the switch manual at the moment, but haven't found anything too promising looking so far. It would seem that some of the SFP ports on the ROACH are noticeably worse than others -- the long cable pretty consistently causes problems everywhere, but if I use only the worst ports with the short cable, they get much better, but far from perfect.
I've twiddled the SFP+ RX parameters on the roach, but to no avail (though I think these only affect the short link between the FPGA and the vitesse tranceiver anyway, I can't see any control ports between the FPGA and the vitesse in system.mhs) Cheers, Jack On 22 July 2014 13:37, David MacMahon <[email protected]> wrote: > 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 >> >
