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Comment by haberman | Hacker News Reader

When I saw this page a few years back I had an idea for a project. I want to create the lowest-latency typing terminal I possibly can, using an FPGA and an LED array. My initial results suggest that I can drive a 64x32 pixel LED array at 4.88kHz, for a roughly 0.2ms latency.

For the next step I want to make it capable of injecting artificial latency, and then do A/B testing to determine (1) the smallest amount of latency I can reliably perceive, and (2) the smallest amount of latency that actually bothers me.

This idea was also inspired by this work from Microsoft Research, where they do a similar experiment with touch screens: https://www.youtube.com/watch?v=vOvQCPLkPt4

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I remember when I got the iPhone X I was so used to higher latency that it felt like the iPhone was typing before I was. It was a very strange sensation until I got used to how quick it was.

If you ever end up doing this project, I find that sometimes it's hard to quantify if something is better when going in the normal-to-better direction, but it's always much easier to tell when something is worse when going in the normal-to-worse direction. So spend a few days or weeks getting totally acclimated to fast response times and then test if you can notice the difference with slow response times.

I like the idea, but note that (1) and (2) can depend on what you’re used to. The fact that one doesn’t notice a handicap doesn’t mean that there isn’t room for improvement, given some conditioning.

I believe there are specific methods to negate these effects (something like going in a specific order with the values)

If would probably be interesting to randomize the latency for certain intervals with some kind of feedback mechanism to provide a blind study.

Sounds like a fun project to do, I wonder if you could even implement it in full discrete logic and skip the FPGA

Is there an appreciable practical lower-bound in latency to that? I’ve never understood how-and-why electronic signals can propagate down a wire so gosh-darn quickly: the speed of sound is what I’d have intuitively expected, not 50-99% the speed of light ( https://en.wikipedia.org/wiki/Speed_of_electricity )

Essentially, energy is carried throughout a circuit by the electric field created by a voltage differential, not by electrons pushing other electrons like how sound is transmitted through a medium. So signals propagate on the same order of magnitude as the speed of light. I think this is a relatively intuitive explanation: https://www.youtube.com/watch?v=C7tQJ42nGno

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