I ask for help because I am not able to solve a problem with my KVM switch and my mouse and keyboard. When my mouse (Logitech G700s) and my Keyboard (Roccat Ryos MK Pro) are connected via the KVM switch (all other USB devices unplugged) misbehave. The cursor lags, the mouse ignores clicks and mouse wheel turns. The keyboard omits letters, prints multiple letters or even a key gets stuck software-wise printing the same letter over and over again until the next key is pressed. When I unplug one of the devices, the problem seems to get better. Right now I have to unplug the mouse to log into my system, otherwise the password will be incorrect, for obvious reasons.
Sometimes the problem is barely noticeable, sometime I can't type two word without three letters missing.
My setup:
I use a (active USB 3) KVM switch with integrated sound car to connect three devices:
- Gentoo / Manjaro / Windows 10 triple boot desktop
- Playstation 4
- Company Windows 10 laptop
Thoughts on my hardware:
I did the following to locate the problem hardware-wise:
- Try all USB ports: problem persists
- Install PCIe USB 3 card: problem persists
- Exchanged the KVM-switch with an other active USB 3 hub and a passive USB 2 hub: same problem
- Unplugged all other USB devices: No help
- Exchanged the cables: same problem
- Did a BIOS update: problem remained
- Tried other mice and keyboards: The lag-rate seems to change a little but the problem persists
I suspect the problem to be a linux related software or kernel problem, although I do not understand at all where it might come from.
Software-wise I did the following:
- Did an update world: no help
- Did a kernel update (gentoo-sources 6.1.67 -> 6.6.21): Same
- Tried older kernel versions (for example 5.4.7): Same
- Checked on processor and memory load when the lags happen: Both are low, no spikes
- Checked on mainboard and processor temperatures: Both are below 40 °C
- Checked dmesg -w: Does not throw errors or messages when lags happen, although at some point during the testing there was a constant reset of one (or more, I'm not sure) USB devices: the mouse. Now it's gone.
- Checked whether the lags occur on terminal (Ctrl Shift F3): Yes they do
- Checked whether the lags occur in Grub (in the Grub terminal): No they don't
- Checked whether the lags increase in number when the system is under load (emerge software): No. Maybe even less but this may be either coincidence or imagination.
Regards
Marius

