I forgot to add this to my posting above...74xx688 (e.g. 74HC688), 8-input magnitude comparator, static (no clocks etc.), inverted A=B output. You may have to shop around to find it in DIL/DIP packaging though. The internal diagram shows how you could build it from individual gates to expand/reduce it. It can be cascaded for more than eight inputs, 16, 24 etc...though be careful of the delay the more you cascade...though it could be done in a parallel fashion if time is not on your side...requires one additional multi-input OR/NOR/AND/NAND gate...as many inputs as '688s...
If you want just a short pulse when A=B changes state in either direction, the old trick of a short RC time-constant on one input of a XOR/XNOR gate, whereas the other is fed direct...but it's another (largely unused) chip.
Steve A.
...just noticed I did attach it before...or at least provide a link...