Keyboard latency
danluu.com
Keyboard latency
1–10 of 274 posts
Re: Keyboard latency
#2IMO, a better measure would be from activation of the switch, as opposed to the beginning of key travel. I don't start waiting for the character to appear on my screen from the moment I begin to press down. My anticipation begins when I feel the tactile feedback of the switch activating (or the switch bottoming out on switches that don't offer tactile feedback). On a keyboard with good tactile feedback, I might not move the switch through it's full travel -- just a little bit above and below the activation and reset points.
Re: Keyboard latency
#3PS/2 keyboards are used by serious gamers because the scan rate is higher than USB.
See https://superuser.com/questions/16893/do-usb-or-ps-2-keyboar...
Re: Keyboard latency
#4PS/2 keyboards are used by serious gamers because the scan rate is higher than USB. See https://superuser.com/questions/16893/do-usb-or-ps-2-keyboar...
For what it's worth, that answer is now 8 years old - I'm curious if this has changed since then.
Re: Keyboard latency
#5On the debouncing thing, Razer announced one with optical switches instead of electrical.
Re: Keyboard latency
#6PS/2 keyboards are used by serious gamers because the scan rate is higher than USB. See https://superuser.com/questions/16893/do-usb-or-ps-2-keyboar...
For what it's worth, that answer is now 8 years old - I'm curious if this has changed since then.
A more recent video claims that the PS/2 advantages are negligible even for serious gamers (around 3:40) https://www.youtube.com/watch?v=AWkvzycD5PE
Re: Keyboard latency
#7IMO, a better measure would be from activation of the switch, as opposed to the beginning of key travel. I don't start waiting for the character to appear on my screen from the moment I begin to press down. My anticipation begins when I feel the tactile feedback of the switch activating (or the switch bottoming out on switches that don't offer tactile feedback). On a keyboard with good tactile feedback, I might not m…
I agree.
Presumably he measured it the way he did because it's easier to measure, rather than because he thinks it's the more meaningful way.
(Though maybe his way is more useful if he's interested in whether a keyboard gives an advantage in gaming, rather than whether it's pleasant to type with.)
Re: Keyboard latency
#8PS/2 keyboards are used by serious gamers because the scan rate is higher than USB. See https://superuser.com/questions/16893/do-usb-or-ps-2-keyboar...
Saying that PS/2 boards are "scanned" is inaccurate, as they trigger an interrupt immediately on a keypress.
Re: Keyboard latency
#9I'm surprised the "humans don't notice 100 ms" argument is even made. That's trivially debunkable with a simple blind A/B test at the command line using `sleep 0.1` with and without `sleep` aliased to `true`. To my eyes, the delay is obvious at 100 ms, noticeable at 50 ms, barely perceptible at 20 ms, and unnoticeable at 10 ms.
Not to mention that 100 ms is musically a 16th note at 150 bpm. Being off by a 16th note even at that speed is – especially for percussive instruments – obvious.
On the other hand, if you told me to strike a key less than 100 ms after some visual stimuli, I'm sure I couldn't do it – that's what "reaction time" is.
Re: Keyboard latency
#10PS/2 keyboards are used by serious gamers because the scan rate is higher than USB. See https://superuser.com/questions/16893/do-usb-or-ps-2-keyboar...
For what it's worth, that answer is now 8 years old - I'm curious if this has changed since then.
I've gotten a FTDI down to 2 ms RTT, so if done right (using isochronous transfer) you can get USB down to 1 or max 2 ms. Looking at the latencies quoted here and in the article it's certainly not the problem.
Notice that just getting a thread scheduled every 2 ms is already impossible for Windows, certainly one running a game. You'll get a bunch of outliers within the second. So even if you got your keyboard down to 5 ms, great, but you are not running an operating system that can reliably do something within that timespan!