Re: 64/66 control code mapping
I know I still have more lab verification, and I know 8B10B is well known/used,
but we have got to do something to slow the XAUI/HARI portion down a hair.
Aside from concerns we have all been addressing, there were two more brought to
my attention yesterday in a customer meeting. The first is if we are worried
about being like Infiniband, and I am not saying we should be and I am not saying
we should not be, but 8B10B at 3.125 in a PC is 'nuts because most PCs barely
pass emissions as it is'. The addition of the spectral content of 8B10B could be
a disater for that interface. We should be careful, if that is one of our
resaons, about trying to be similar to an interface that most likely will have to
The second actually bothered me more because I never thought about it and have to
do some more verification to determine validity, but the customer pointed out
that only fr-4 was readily available in his country, where as some of the
materials I have been using was very difficult for them to find. That being
said, with respect to skin effect of the geometry and the erratic loss tangency
of fr-4 ( the real part isn't pretty either ), the slower speed can make a
> If it appears that 8B/10B is no longer desirable due to EMI and skin-loss
> limitations on the PCB, we will be quite happy to present our ideas w.r.t.
> using 64b/66b on the 4 XAUI lanes.
> Rick Walker