Dear Tomaš, thank you so much for your support, thanks to you I felt encouraged to finally update my BIOS. It solved the driver problem (and by the looks of it, improved fan performance, but it's handwaving); however as far as I can tell from dmesg and system performance, only one core is used still. If you have any great hints or suggestions about how to proceed, please share those.
New Xorg.0.log (initial issue resolved): http://f.nn.lv/n5/7h/yq/Xorg.0.log New dmesg output (still only one CPU found): http://f.nn.lv/n5/7h/zi/dmesg.full
