Model A1225 / Early 2009 / 2.66, 2.93, or 3.06 GHz Core 2 Duo processor

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Won’t boot from new SSD

I have a 24” 2009 iMac that I’m trying to replace the original HDD with a Western Digital Blue 250GB SSD.

With the SSD in an external case the iMac sees it just fine and I was able to install OS 10.11 on it and even boot from it that way.

When I install it in the iMac it won’t boot from it at all. I just get a white screen with no flashing question mark??

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After further research and tinkering it turns out I needed a new Sata data cable. Apparently it provided good enough signal to work with the slower data rates of a hdd but not a new SSD. Hence the red cable.

I will do a better job of rerouting and installing when I’m ready to reassemble but yeah, new cable...

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Bet you didn't remember to format it GUID Mac OS X Extended before you put a system on it. The Mac doesn't how it's formatted externally. It does care when it's internal.. Remember to address the thermal sensor issue with one from OWC if you haven't. Run away fans may ensue if you don't.

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I did format as GUID Mac OS X Extended.


Glad you solved your problem. Come back if the fan starts bothering you. Would you mind telling others exactly where you got this cable and what it was.


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abrixen will be eternally grateful.
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