RE: CPCI term resistors

["Ingraham, Andrew" <Andrew.Ingraham@compaq.com>]

>  CPCI is meant to be used for the backplane and the lengths are extremely
> large. reflected wave switching cannot be used and needs the terminations
> on
> the bus.
 
Actually, I think CPCI uses reflected wave switching too.  After all, it
uses the same silicon.

It just has those extra damping resistors which helps make the reflected
wave more "ideal".  The ideal would be no more than one reflection, just out
and back, one round-trip bus delay.  Partly because of the stubs in normal
PCI, sometimes you need to wait for a few reflections to die down before the
signals can be called stable.  At 33 MHz, the 10 ns allocated to bus
propagation time gives you time for several reflections.

Andy