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Mid 2010 Model A1278 / 2.4 or 2.66 GHz Core 2 Duo processor

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Keeps showing a circle with a diagonal though it

Trying to boot to a mac os yosemite usb stick, every time it fails, :/

Also whats the highest macOS it can run,

ALSO thanks in advance :]

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When trying to make installer the 2nd time

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Sounds like you may have not prep’ed the thumb drive correctly.

First you need to format it using a Mac with a GUID Journaled file system. Next you need the correct OS installer copied to it.

The highest your system can handle is macOS High Sierra (10.13.x) but I strongly recommend sticking with Sierra (10.12.x) as High Sierra alters the file system from HFS+ to APFS which does not run too well on older SATA based drives. Get the installer from here: How to get old versions of macOS older installers have an expired certificate.

Follow this guide to setup the installer onto the thumb drive How to create a bootable macOS Sierra installer drive

Last step if the drive won’t boot up on its own with the thumb drive, time to restart your system and press the Option (⌥) to get to the startup manager so you can select the thumb drive.

Reference: Mac startup key combinations

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9 Comments:

I feel so stupid right now, XD

Thanks @danj

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@beanman56 - Let us know how it goes!

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@danj I can't make the installer,

on my two other macs it didn't work

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@beanman56 - Well you need to explain why it didn't work

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On macdaddy.io's application,

It ALWAYS make bootable mac os usb sticks

But with sierra it keeps saying

"An error occurred.

Try ejecting the destination disk and reinserting it, or rebooting. It probably couldn't be unmounted to erase it."

BUT in disk utility it can unmount with no problem

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A prohibitory symbol, which looks like a circle with a line or slash through it, means that your startup disk contains a Mac operating system, but it's not a version or build of macOS that your Mac can use.

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Ben Capehart will be eternally grateful.
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