I've a GA-Z97X-UD5H with i5-4690K and two 1920x1200 displays attached to the mobo driven by the integrated Intel HD 4600. The system worked reliably for years until I upgraded to Hi Sierra. (I had been planning to skip HS but then Meltdown/Spectre happened.) I used the Direct Upgrade guide with success. In EFI/CLOVER/kexts/Other I have FakeSMC.kext AppleIntelE1000e.kext AtherosE2200Ethernet.kext In the days since the upgrade the system froze 3 times. In each case I had a typical set of apps and windows open. The first freeze happened when Google Chrome was in the foreground and I was browsing a netdata dashboard. The second two were both today while I was editing in MacDown. I can find nothing in the logs that seem related to the problem. How can I debug this? What might I try to mitigate the problem?