I'm running into the same issue. Tried Kernel 4.4-rc5, would also not boot without acpi=off and nomodeset.
After booting with those two parameters, the GUI is very sluggish, animations take on the order of seconds. Also lost mouse and keyboard (wireless) functionality when upgrading - possibly unrelated. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1525615 Title: Ubuntu not booting on iMac 5K with ACPI enabled To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1525615/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
