A WD My Passport hard drive (bought in 2016-7) can be detected by one Macbook (a 2018 15" MacBook Pro) but not another (not even in diskutil) (a 2013 11" Macbook Air). What is the explanation for this? Has it got to do with something along the lines of differences in design in the motherboard (eg. different voltage ranges for logic levels)

  • What is the version of macOS running on each one of the MacBooks?
    – Nimesh Neema
    Jun 1, 2019 at 8:51
  • Can you tell which HardDrive is the other??or even the format of it??
    – user297492
    Jun 1, 2019 at 10:54
  • I would tend to think that there is a (hardware) issue with one (or more) of these devices. The drive could have a controller that is just enough out of spec that the older Mac doesn't like it. Do you have access to and the ability to try the drive itself in another enclosure? Jun 1, 2019 at 10:57

1 Answer 1


The common cause of a bus powered drive not operating is the computer isn’t getting enough power through the cable you are using to power the unit.

Swapping cables or using a powered hub or getting a new enclosure can help triage and isolate why this happens in many cases. Also, looking for a long running fsckprocess I’m case the “good” mac is actually triggering an “unclean mount” type check. That often delays a device from mounting, but you should see it in diskutil immediately which doesn’t match your case here.

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