Use fast driver with old slow bus?

From: vax3900 (vax3900_at_yahoo.com)
Date: 06/22/04 

Date: Tue, 22 Jun 2004 11:56:21 -0400

I want to find proper driver chips for an old bus (Q22Bus). The protocol
says: rise/fall times must be no faster than 10ns. The chip I am evaluating
is 74lvt125. It meets all other requirements but the rise/fall time is much
faster than 10ns. It is not stated in the data***, but it would be around
1 ns if we look at the propegating delay time (1ns~4ns). I know there is
potentially signal reflection problem. But how bit the risk is? The Q22 bus
is a terminated bus, with resistors of 178 to 5v and 383 to gound for one
type and 330 to 5v and 680 to gound for another type. The length of the
backplane is 10 inches and maximum total length of 16 ft cables can be used
to connect several backplanes. I wonder if I use this chip to drive the
bus, is the total length of cables the only facter I need to sacrifice to
avoid problems? Are there other problems that I am not aware of? Thanks. 

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