Microsoft's Spectre And Meltdown Patches For Windows Are Bricking Some AMD PCs | HotHardware
Headline says it all. Apparently the systems with the (old) AMD processors that are being bricked aren't vulnerable to the flaws in the first place - so they don't even need patching! Microsoft have now put a brake on the update so that it aborts if it recognizes certain non-Intel microprocessors.
I love the comment complaining to Microsoft that says, "I understand that making the machine unbootable is the best protection from remote exploitation, but I would rather have the OS working."
There's also some trickiness about certain anti-virus software preventing the update from being applied - the only Windows PCs I use have the standard Microsoft anti-virus stuff (defender or Security Essentials) so they've been okay.