I did some further testing and it seems I have found a culprit and a solution. In older kernel versions (3.19.8 and 4.0.9 worked flawlessly without extra boot parameters) I get something like this when booting:
ACPI BIOS Warning (bug): 32/64X address mismatch in FADT/Pm2ControlBlock: 0x00008800/0x0000000000008100, using 32-bit address But in newer kernel version the behavior has changed so that it instead uses 64-bit adress! This is solved by adding the boot parameter "acpi_force_32bit_fadt_addr" and voilá, the problem is gone. So why has the default behavior changed, and why must it be up to the user to set the workaround in kernel options? Couldn't the kernel detect the hardware and use 32-bit registers itself? Additionally, for this machine to work properly with 4.4.0-34 I must add noapic or/and nolapic to boot parameters. Otherwise, the fan is at max speed all the time and the computer gets very sluggish, it fails to reboot properly - however the disk benchmark test works fine. I suspect I shall have to open a different bug report for these issues. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1590154 Title: System slow unless using touchpad To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1590154/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
