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Why Modern Computers Struggle to Match the Input Latency of an Apple IIe By Joel Hruska — “The system with the lowest input latency — the amount of time between when you hit a key and that keystroke appears on the computer — is the Apple IIe, at 30ms.”

There is a table of measurements that included latency, clock speed and computer year. It doesn’t include the TRS-80 nor list CPU so you can’t tell how much latency is based on system design or CPU design or other factors. The table does list the number of transistors in the CPU’s under test. “the color coding shows that chips with higher numbers of transistors tend to be in systems with more latency, and faster systems tend to be older than slower ones.”

An Apple IIe isn’t handling sophisticated multi-tasking commands. It isn’t juggling background threads, or dealing with multiple applications that aren’t designed to be aware (or careful) of one another. It isn’t polling a huge array of devices that range from audio and network controllers to discrete GPUs and storage. The Apple IIe OS doesn’t use a compositing window manager, which adds latency. This article, by Pavel Fatin, is an in-depth breakdown on latency processing and discusses how each much delay each step in a modern system adds, from keyboard scan to final output.

Latency is a big issue in movies as well as people notice when the lip sync gets too far off. Typists learn to touch type and that doesn’t involve latency except that the machine can keep up. Virtual reality, gaming, and graphics can make latency critical for error reduction. The real question is how much is OK and how much is too much. Human’s have latency, too,