Thanks for the info, I will certainly try and get my hands on some new Mellanox firmware before fighting with the vitesse.
Cheers, Jack On 23 July 2014 01:04, Jason Manley <jman...@ska.ac.za> wrote: >> though I think these only affect the short link between the FPGA and >> the vitesse tranceiver anyway, > Yep, you've got the right of it. You'll need to tweak the Vitesse PHY through > the control interface from software; there is an MDIO interface available, > which does work. But we don't have a full datasheet for the part and so can't > offer a clear solution for you. There are a LOT of parameters to tweak; not > just a generic "RX equalisation" knob like on the Xilinx, for example. I > recall a multi-tap filter chain, gain, feedback loops and other trickery on > the RX side. So we've just left it on defaults, but it's definitely not > optimal. > > The Mellanox ASICs are the only ones we've had trouble with (all Broadcom > based switches seem to work fine with 3m cables, for example) and Mellanox > have a software fix for the issue, by tweaking their own PHY TX parameters. I > believe this fix will be in their "General" firmware release soon (though no > date has been promised yet). Until then, I suggest you ask for an > early-release/testing firmware. > > Jason
