MBP 2018 - Restarting during external boot normal?

Discussion in 'MacBook Pro' started by duckrabbit, Feb 9, 2019.

  1. duckrabbit macrumors member

    Jun 21, 2012
    I've been testing my bootable backup with my MBP 2018, and I've noticed a peculiar behavior that wasn't present on my 2012 MBP.
    • When I first restart after changing startup disk, the machine will restart itself once early on in the boot process. If changing startup disk via System Preferences, this will occur shortly after the Apple logo appears. If changing disk via Startup Manager menu (holding option on boot), this will occur immediately after selecting the new disk. The machine then proceeds to boot from the desired disk.
    • The restart does not occur if I continue to restart using the same disk. It only occurs on first restart after selecting a new disk.
    • This happens even when switching back to the internal drive.
    Startup security settings have Secure Boot set to "full security" and External Boot set to Allow.

    Has anyone else noticed this behavior?
  2. duckrabbit thread starter macrumors member

    Jun 21, 2012
    I've confirmed it doesn't happens if I plug the hard drive into a powered USB hub (it's a bus powered drive).
    So I guess these new machines don't boot from bus-power as well as the old ones...
  3. Ploki macrumors 68040

    Jan 21, 2008
    Not exactly the same, but similar.
    after i boot from external USB, if I shut the system down and power it back on it will boot shortly than turn itself off again. i have to boot it again after
  4. duckrabbit thread starter macrumors member

    Jun 21, 2012
    Yeah sounds like the same issue. After some more testing, I've found the exact behavior is drive dependent. I have a second drive that works perfectly and a third one that almost never works unless it connected through a powered hub.
  5. Ploki macrumors 68040

    Jan 21, 2008
    hm, i will try different ports. I only have one bootable external drive tho

    the odd thing is, restarting works fine when booting off external.
    and i don't remember this happening on 10.14.2, i would have noticed

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