Dan Luu measured the input lag, or latency, of keystrokes across a variety of hardware ranging from an Apple II and a TI-99 up through modern Lenovo ThinkPads, with interesting systems like an SGI Indy, a NeXT Cube, a Commodore Pet and others.You might be surprised by how fast it is compared to, say, a basic iMac today, despite orders of magnitude difference in hardware power. Bill Atkinson's (true) genius of a graphics system was incredibly fast, and modern overhead is vastly more draining and complex.
Computer latency: 1977-2017
The lowest latency devices were mostly the oldest. An iMac G4 running macOS 9 had only 60% the latency of the machine running OS X.
He also tested mobile devices' scroll latency. Apple's iDevices absolutely demolished all Android-based devices. Oddly enough, only a Gameboy Color from 1998 could match them.
The whole thing is great, but of particular interest are his analyses of the Apple II, the iOS rendering pipeline, and of general system complexity.