It's a 2017 article, but according to this, the two personal computers with the lowest input latency of all time are the Apple //e (1983) and the TI-99/4a (1979)
In particular it's the depth of the abstraction stack divided by transistor count. Wirth's Law: "Software is getting slower more rapidly than hardware is becoming faster."
[–] cowlevel 2 days ago
[–] FabHK 2 days ago
https://en.wikipedia.org/wiki/Wirth's_law