tedaste, this would appear a two part problem (acpi and graphics), but let the initial focus be on the first issue of not able to boot up at all without acpi-off. Hence, the issue you are reporting is an upstream one. Could you please report this problem following the instructions verbatim at https://wiki.ubuntu.com/Bugs/Upstream/kernel to the appropriate mailing list (TO Rafael J. Wysocki, and Len Brown, CC linux- acpi)?
Please provide a direct URL to your post to the mailing list when it becomes available so that it may be tracked. Thank you for your understanding. ** Changed in: linux (Ubuntu) Importance: Medium => High ** Changed in: linux (Ubuntu) Status: Incomplete => Triaged ** Summary changed: - Ubuntu not booting on iMac 5K with ACPI enabled + [iMac17,1] Not booting with ACPI enabled -- 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: [iMac17,1] Not booting 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