I'm developing on a small modular computer system using the Z80 just for fun. The backplane is a prototype PCB with five DIN41612 connectors wired in parallel, running about six inches from the first connector to the last. (This one: http://www.busboard.com/BB3U)
The CPU card I've made is composed of 74HCT-series logic and CMOS components (for SRAM, Flash, Z80, UART, etc.) all running at 5V. What kind of termination on the backplane would be ideal for a system like this?
The fastest signal on the bus is a 20 MHz system clock, everything else is in the 5 MHz range. The signals are mostly unidirectional, a few bidirectional for the data bus, and then some open drain signals for reset and interrupts inputs to the CPU card.
I've read about the VME bus which used Thevenin termination and it required strong drivers (74F-series to sink/source 24mA) over a very long backplane so that seems inappropriate here. But I'm not sure what else is appropriate.