I have just installed Ubuntu 18.04 in a computer that has an ASRock EP2C602-4L/D16 motherboard with two Intel Xeon E5-2660v2 CPUs and 128 Gb of DDR3 RAM. Ubuntu is installed in a 1Tb SSD.
Everything works well, with one exception: keyboard and mouse input in the initial login screen are extremely slow and lagged. By that I mean the following. Specifically at the first login screen after boot, when moving the mouse, the mouse cursor responds with huge lag and when typing (for instance, my password to log in) the characters appear also with huge lag. Longing in is a true nightmare.
The problem does not happen after logging in or if I go back to the login screen (for instance after a screen lock or after recovering from a power suspend time).
I have searched a lot online for solutions to this problem. There are related questions about this that were asked previously. For example, this one, this one and this one. In my case, however, I have no issues with CPU overworking or overheating. Changing the settings of mouse and keyboard rate for the root also does not help.
Because the issue happens only at the first login screen after boot, I figured it could relate to video driver initialization. Hence, I added nomodeset to the kernel, updated the grub and restarted. To my surprise, this led to two results: (1) the login screen now worked perfectly well but (2) keyboard and mouse became extremely slow / lagging after login (the screen also started to refresh from bottom up very slowly from time to time, also with some flickering). So it seems that the original issue was indeed related to video card drivers, but I have no idea why them are not being properly initialized after login with nomodeset quiet splash.
My video card is onboard and its driver version is 3.3, which seems to be up-to-date. So my question is simply how could I solve this and have my mouse and keyboard work properly both in the login screen and after login?
