[SI-LIST] quenching ugly spikes?

Hi!

As a hobby I'm designing an Ethernet/USB board for those Atari computer
enthusiasts who are still active. My board sits on top of an accelerator
board containing an MC68060 and a couple of CPLDs, connecting to my board
through two 2.54mm (0.100") 2x25 pin connectors (one for data lines and one
for address/control). My problem is that I get really ugly signals from the
accelerator board. They are supposed to be 3.3V signals but I see spikes all
the way up to 6V on the address lines and the data lines start off with a
small 2V top, then down to -1V and finally up to a 5.5V spike before
settling at 3.3V after a total of 18ns. I assume that these symptoms are
caused by two things:

1) There are no series resistors on any lines on the accelerator board, and
the data lines are as long as 22cm (about 8.5"). The rise times are
somewhere in the 2-3ns region, so I suppose the lack of series termination
is not a good thing. I have series resistors on my board and when my board
drives the signals they look much nicer.
2) There are only two ground pins at each end of both connectors, in total
four per connector. The lack of nearby ground pins for the data and address
lines isn't good either?

What do you think I can do about this? I've tried terminating using diodes
(though only 1N4148) but that didn't change anything. I'm thinking of using
chokes on the lines. Could that be a good solution?

Both my board and the accelerator board are four layer boards with dedicated 
ground and power layers.

I hope you can help me out! :)

Thanks!
/Henrik Gildå


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