Bloody hell, Bart, using FAST-TTL in combination with breadboard design, this I call 'brave'....

Your breadboard design with these many wires introduces so much inductivity, that use of FAST-TTL results in monstreous ringing. Like Erik told, ground-bounce is the major issue, here! Only by using solid ground plane inductivity of ground routing can be kept minimal. Of course, also power supply decoupling directly at each chip is needed.

If you cannot use PCB containing solid ground plane, you should not use FAST-TTL!! 74HC(T) is a good choice, also 74LS.

Unfortunately, things are so complicated, that even by taking an oscilloscope you probably won't see what's actually going on with your circuit. It's hard to distinguish ground bounce from eroneously connected scope-probe, which presents some ringing! Also, ground bounce occurs INSIDE chip, too, and will never be observed by a scope...

When working with fast microcontrollers you finally should switch from breadboard design to double sided PCB, containing solid ground plane!! This is especially valid, when your circuit contains extended address bus and data bus!!!!!

Good luck,
Kai