4 ms·
Many CPUs have USB support. Pin count also doesn't correlate to latency, what matters is the minimum buffer size and transfer speed. USB can beat PS/2 for late
by duped 5y ago
Many CPUs have USB support. Pin count also doesn't correlate to latency, what matters is the minimum buffer size and transfer speed.
USB can beat PS/2 for latency without issue.
- WithinReason 5y agoIsn't PS/2 interrupt based, while USB is based on periodic polling?
- duped 5y agoPolling is often lower latency than interrupts on modern hardware, since it can run at much finer grains and has so much less overhead to startup over an ISR.
- wtallis 5y agoThat's often true on a scale of microseconds, but USB input devices are polled at intervals on millisecond scale.
- cma 5y agoOnly in the slowest modes. It is possible to go faster than the 1ms poll rate, though it is back to interrupts: > Transaction latency > For low speed (1.5 Mbit/s) and full speed (12 Mbit/s) devices the shortest time for a transaction in one direction is 1 ms.[6] High speed (480 Mbit/s) uses transactions within each micro frame (125 µs)[7] where using 1-byte interrupt packet results in a minimal response time of 940 ns. 4-byte interrupt packet results in 984 ns. https://www.wikipedia.org/wiki/USB_(Communications) https://www.wikipedia.org/wiki/USB_(Communications)
- bschwindHN 5y agoBen Eater has a good video on this: https://youtu.be/wdgULBpRoXk?t=1765 https://youtu.be/wdgULBpRoXk?t=1765