On 23/1/21 9:54 pm, Russell Coker via luv-main wrote: > https://www.overclock.net/threads/ps-2-keyboards-vs-usb-keyboards-latency. > 1730550/ > This is one of many pages discussing the issues of USB vs PS/2 keyboard > latency. Apparently PS/2 keyboards will increase the latency by 5ms (at > best) > and USB by 1ms if tweaked. USB 3.x apparently gives the best latency.
The keyboards and mice I have tested are at best only USB 1.1 speeds (12MB), but I don't think that is the bottleneck for latency, as they can still be polled at 1kHz. However, with the slower USB 1.0 devices, you will find that Linux sets the bInterval to 10ms, which I imagine would work out to 8ms in practice, as that is the USB 1.0 frame interval. I have one mouse where it is switch settable on the mouse - a bit of a gimmick, but a lower rate can be helpful for reducing CPU in some apps where a mouse movement is triggering redraws. Other latency factors can be external hubs (though anything less than USB 2.0 would be unusual now), and whether there are many high-bandwidth devices sharing the same root hub. Another factor for keyboards is how many keys rollover they have - I notice that one of my keyboards presents as a dual HID device. I'm not sure I want a high n-key rollover if I can't guarantee the order of the keys, though if you were mashing the keys in a game you might not care. Glenn -- pgp: 833A 67F6 1966 EF5F 7AF1 DFF6 75B7 5621 6D65 6D65
OpenPGP_signature
Description: OpenPGP digital signature
_______________________________________________ luv-main mailing list -- [email protected] To unsubscribe send an email to [email protected]
