Strange boot problem with Mid 2010 Mac Pro desktop running OS X El Capitan

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Strange boot problem with Mid 2010 Mac Pro desktop running OS X El Capitan

I'm experiencing a strange boot-up problem with my mid-2010 Mac Pro desktop computer.

When performing a soft reboot (Apple Logo --> Restart...) my computer will shut down and begin the reboot sequence as usual (chime, Apple logo, progress bar), however a little passed the half way point of the progress bar, I get a greyed-out prohibited symbol (circle with a diagonal bar through it) and nothing more happens.

However, if I press the power button for a second or two and shut the computer down manually, then restart it by pressing the power button again, the computer boots up just fine.

I've tried a PRAM reset to no avail.

I then installed a fresh version of El Capitan on one of my internal SSD drives (I have two installed) then restarted using the new install to run disk utility's First Aid function on the primary drive. The problem is still present.

Does anyone have any experience with this and what could be going on?

Mac Pro, OS X 10.11

Posted on Mar 21, 2020 4:30 PM

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Answer 1

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orangegrouptech

Level 4

1,858 points

Mar 21, 2020 6:56 PM in response to MichaelNicola

Do you have any other macOS volumes (partitions) or any other hard disks you plugged in containing OS X?

the prohibitory symbol means you are trying to boot a version of OS X that your computer doesn’t recognise.

Try unplugging all hard disks you have plugged in, or use the option key when booting (when it chimes quickly press and hold option) and select your boot disk and press enter.

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Answer 2

Mar 21, 2020 7:56 PM in response to orangegrouptech

I have two SSD drives inside this Mac Pro, both 1tb Samsung QVO drives. One contained the operating system (OS X El Capitan) while the second was left blank - I left it as a scratch disk for Photoshop; both drives only had a single partition on them. There was only one OS in this system, which is why this prohibitory symbol was so confusing once I researched what it meant.

Earlier today, however I did install a fresh copy of El Capitan on the second SSD (the scratch disk one) so that I could boot up in it, and run Disk Utilities' First Aid on the primary drive in an effort to try and fix whatever was causing the issue. That worked fine and Disk Utilities did it's thing. However, when I booted back up using the primary drive, I encountered the same behavior (prohibitory symbol on soft restart, but working on hard restart).

And to make matters even more confusing, I just ran a software update on the fresh El Capitan OS I installed earlier today on the second SSD, and now it's doing the same thing!

I'm starting to think this computer does not like these particular SSDs I've installed. Good thing I've kept the original HD; I may pull out both SSDs and reinstall the original HD tomorrow morning and try these tests again.

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Strange boot problem with Mid 2010 Mac Pro desktop running OS X El Capitan

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