What is the maximum length a MC68030 can be placed away from Commodore CDTV motherboard, without affecting timings?
You are talking about adding 0.5 nanosecond of delay. With the slow edges, that should be still fine.
You also are talking about adding 100+ nanoHenries of inductance; I use 25nanoHenry/inch as rule of thumb.
To survie that, add 0.1uF across VDD/GND pairs that power the 68030. You must install these capacitors right at the DIP pins
And clock lines could use 220 ohms in series, to dampen overshoots, in either direction.
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The ground pin has to handle all the fast IN/OUT currents. So make the Ground extension be a wide piece of braid, or a dozen stranded wires all in parallel.