The new OS X 10.10 Yosemite was received pretty well upon release, sure it had a few minor hiccups, but overall it was an improvement. But not everything is visible right away, especially not when it’s done in secret.
Apple has silently and without any warning killed support for third-party SSDs in this new OS X version, leaving anyone who uses such as a boot drive and has TRIM enabled with a Mac that won’t start. The cause for this is the new Kext Signing security-feature that checks if the system has been altered and has parts approved by Apple. In itself, this is a great feature and one that won’t effect the average Apple user, but professionals with customized high-end Mac’s might be left with a lot of trouble.
“Kext signing basically works by checking if all the drivers in the system are unaltered by a third party, or approved by Apple. If they have been modified, Yosemite will no longer load the driver. This is a means of enforcing security, but also a way for Apple to control what hardware that third-party developers can release OS X support for.”
The good news is that you can disable the Kext signing and the Trim Enabler tool has been updated to do just that. It however has the downside that none of your drives are protected by this feature as it’s a global setting and not per drive. The blog post about this issue by Cindori Software, the makers of Trim Enabler, also has a guide on how to get back into your system if the Yosemite update should have locked you out due to a 3rd party boot drive.
Thanks to Cindori for providing us with this information