[kragen]

Sorry I hadn't responded until now!

It wouldn't be much more complexity to make the VT52's increment sequence a linked list instead of a counter, another 24 bytes of RAM or maybe just 120 bits. The escape sequence dispatch microcode is probably more space.

I hadn't thought about the complexity of PS/2 decoding.

My thought with the 4-LUT equivalency is that if you take some arbitrary 4-input combinational logic function and build it out of things like ANDs, ORs, NANDs, and inverters, you're going to need about 4 gates on average, which is about one 7400-series chip. I agree that things like bidirectional shift registers and up-down counters are hungrier. And maybe I'm underestimating what fraction of the VT52 consisted of such things.