APPLE HAS QUIETLY DISABLED software driver support for third-party solid state disk (SSD) drives in Mac OS X 10.10 Yosemite by default, leaving some unsuspecting Mac users with third-party SSDs as boot drives unable to boot their machines.
Mac users who have Apple SSDs in their machines won't notice, of course, but the change can present a vexing problem for professional Mac users like graphic designers and video editors who have Macs with third-party SSD drives installed and use the third-party Trim Enabler software driver.
Cindori Software markets the Trim Enabler SSD utility and has documented the Yosemite third-party SSD problem in a blog post.
The firm explained that Yosemite includes a new security feature called 'kext signing' which validates all kernel extension software drivers before loading them.
"Kext signing basically works by checking if all the drivers in the system are unaltered by a third party, or approved by Apple," said the blog post.
"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 third-party developers can release OS X support for."
Cindori Software has updated Trim Enabler so it can turn off kext signing, but noted that doing so disables the security feature because it's a global setting.
The firm's blog post further explained: "It is important to note that disabling the kext signing to enable Trim is best described as taking a sledgehammer to crack a nut, and for most users it will not be worth it.
"But I have been unsuccessful in creating a less invasive method to enable Trim, as all of Apple’s AHCI SATA drivers are closed source and undocumented, which makes it impossible for me to create my own Trim driver and get it signed. This is the only alternative for enabling Trim for the moment.
The post added that the problem will not get fixed unless Apple changes its policy. This is because Apple keeps its AHCI software driver for SSDs private, locking out developers of third-party SSD support software.
The blog post includes instructions for recovering a Mac system that is unbootable after updating to Yosemite. µ
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