Re: Microstrip line for PCI clock !!?

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

> But what about PCI extenders?
> one can make a PCI card with the correct length, but there are some
> motherboards/small PC cases that use "passive" PCI extenders.
 
If the motherboard was designed to use the extender or "riser" card,
there is no issue.  You start measuring your 2.5" clock length where the
end-user's PCI card is supposed to plug in.  Treat the riser card as
part of the motherboard, which just happens to be physically two pieces.
The system designer needs to control his clock lengths on both.

If you use a passive PCI extender card in a normal PCI connector, say
for debugging, then it will skew the clock late.  It might not work.
But it probably will; 33 MHz PCI is somewhat forgiving.  Since the AD
and control lines got longer too, it probably won't violate input Hold
times; but input Setup times for signals driven from the card plugged
into the extender, might be violated.  At 33 MHz, there is lots of time
available so an extra nanosecond or two might not "break" it.  Anyway,
for debugging, you accept the fact that what you have is non-standard.

Andy