Hard drive works in external enclosure but not in Mac Pro

Discussion in 'Mac Basics and Help' started by Moof1904, Aug 20, 2009.

  1. Moof1904 macrumors 65816

    May 20, 2004
    This is strange. I have a SATA drive that works when it's in an external USB enclosure but when I put the same SATA drive in one of the bays in my Mac Pro, the Mac Pro won't start up.


    -I've reformatted the drive (with GUID and with Mac Partition Map), with no change in behavior

    -A different drive in the same Mac Pro drive bay works fine, so it's not the drive bay

    -the suspect drive in any of drive bay keeps the computer from booting (grey screen, no apple)

    -the suspect drive works fine (and tests fine with disk tools and Drive Genius) when it's in the external USB enclosure


    What would make the drive work fine in an external enclosure yet prevent the Mac from starting up when it's put into a drive bay??!?!?!
  2. rjheys macrumors regular

    Aug 9, 2008

    It sounds like the Mac Pro is trying to boot to the new drive whenever it is inserted. Try holding down the left alt key when you start the machine, this should bring up the selection of bootable drives, then just select your normal HDD.
  3. jpyc7 macrumors 6502

    Mar 8, 2009
    Denver, CO
    I don't know much about SATA drives, but there used to be things like "master" and "slave" modes for older hard disks where one had to set jumpers and such. You might be running into such a problem, if your two disks inside are conflicting. Especially if the Mac won't even boot.
  4. rjheys macrumors regular

    Aug 9, 2008
  5. Moof1904 thread starter macrumors 65816

    May 20, 2004
    Thanks for the suggestion

    I'll give your boot idea a shot now that I'm back in the office.

    No. It didn't work. I've been running a disk verify function in Drive Genius for four hours and it's found nothing wrong. When I removed the drive just now after trying your suggestion, I moved a different drive from bay 3 into bay 2 and the different drive works just fine in the same bay. So just I've re-confirmed that it's not a problem with the drive bay.

    I also added a completely different drive into the open bay and works fine, too, so it's not a problem with the Mac working when three bays are full but not working when four bays are full. It's this drive: no matter how a reformat it, the drive checks out fine but the Mac won't boot with the drive in it.

    What's going on with this drive that completely hoses the Mac when it's internal but it works fine in an enclosure?

  6. Moof1904 thread starter macrumors 65816

    May 20, 2004
    One more piece of information, in case it's helpful:

    when the Mac tried to start up, I get only the grey screen and a cursor. The apple doesn't appear. Does the presence of the cursor suggest that the Mac is booting up to a certain point and stalling or does the cursor appear as soon as the grey screen does?

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