Update on Trim in Yosemite

Update on Trim in Yosemite
July 30, 2014 Oskar

This is an old post. Please see the latest post on Trim in Yosemite:





The state of Trim in Yosemite

As some users may have noticed, if you try to enable Trim on OS X Yosemite, you can get stuck with a grey screen with a stop sign during boot. And as detailed in these two posts., this issue was due to a new feature in OS X Yosemite.

In OS X 10.10 (Yosemite), Apple has introduced a new security requirement called kext signing. (A kext is a kernel extension, or a driver, in Mac OS X)

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 step by Apple to lock out anyone from making software that interacts with the system, to make the Mac experience more and more similar to iOS.

Since Trim Enabler works by unlocking the Trim driver for 3rd party SSD’s, kext signing prevents Trim Enabler to enable Trim on Yosemite, at least out of the box.

Currently, there is only one way to continue to use Trim Enabler and continue to get Trim for your third party SSD, and that is to disable the kext signing requirement.

While it is unfortunate to have to disable kext signing, it still leaves you with the same amount of security as in OS X Mavericks, where the kext signing requirement didn’t exist.

Trim Enabler 3.2.5 Update

I have released a Trim Enabler 3.2.5 update, which is adapted for Yosemite:

  • Trim Enabler can now disable kext signing in order to enable Trim on Yosemite
  • Fixed an issue with Trim Enabler not launching on Yosemite DP4 / Beta

Apple is locking down the Mac

It’s becoming clear that Apple wants to block applications from altering the OS X experience. While disabling kext-signing still allows Trim Enabler to work, I wish the process of enabling Trim would be smoother. The first thing that comes to mind is to create a kernel extension that somehow achieves this purpose. But as detailed here:

Kext signing means that a valid, signed kernel extension can only be created with a certificate provided by Apple as part of their $99/yr Developer program, and additionally that interested parties must fill out a special form explaining why they require the certificate; kext certificates are only provided upon request and approval.

Apple now effectively controls which kexts are allowed on OS X, and thus, what features that developers like me can release for OS X. And since Apple has made such an effort to block third party SSD’s from getting Trim support in OS X, my guess is that if someone were to make such a kext, Apple would deny a certificate, making it impossible to distribute. So for now, using Trim Enabler 3.2.5 and later is the best way to enable Trim on OS X.

I believe that Apple’s new direction for OS X is unfortunate and ultimately will end up greatly limiting Pro users in favor of usability for casual users. I don’t think it’s long before we will have to start “jailbreaking” our Macs as well.

Recovering from stop sign on boot screen

For those who are stuck on the grey boot screen, here’s how you get back into OS X:



If you want to discuss Trim Enabler and Yosemite, use the sticky topic on the forum: Trim Enabler in Yosemite


  1. Doug Anson 2 years ago

    First, thanks for the great software… its worked fantastic up to now!

    I would heartedly suggest that you not disable the kext security extension – un-signed (and hence “unblessed”…) kernel drivers are exactly why Apple has elected to enhance protection of its customers by *requiring* signed drivers. Having customers turn that off just for trim feels like a really bad idea… imo.

    Instead, why not get TrimEnabler signed and made “official”? ($99/yr is not that much for Cindori). If it happens to be that Apple has issues with the driver that is submitted, then it may be a good (for both Cindori’s customers as well as Apples’) to get those issues rectified and “blessed”. I know that’s probably the “long hard road”.. but it may be the best in the long run… just a thought.

    • Frans Zantvoort 2 years ago

      I can only support that. I will do without Trim Enabler now.

    • Robert Lee-cann 2 years ago

      I think Cindori would probably have considered doing this, and as Mac developers have likely already paid their $99/year for Apple Developer membership.

      The problem is, that it’s highly unlikely that Apple would approve a kext security extension that allowed third party SSD to run on our Macs. If they didn’t want to lock us into their hardware, and their hardware only, then TRIM would be enabled automatically for every drive that supported it.

      So, here we find ourselves, stuck between the decision to run with kext security disabled, or with TRIM disabled – the latter that will greatly reduce the lifetime of our SSDs.

    • Author
      Oskar Groth 2 years ago

      Trim Enabler is not a kext.
      Trim Enabler modifies an Apple Trim kext, thus breaking the signature.
      All AHCI SATA API’s in OS X are private and undocumented. There is no way to write a Trim driver without writing a completely new AHCI driver.
      So the issue is not with me being cheap about the $99. I am already paying that, to get the app code signed.
      The issue is that it’s not possible to create, and sign, a kext that enables Trim.

  2. andrew c 2 years ago

    I’ve tried the procedure listed above to recover from the stop error. No dice. Tried every recommended approach in the forum. Still stuck. I’m now down to reinstalling osx and will likely lose many of my custom configurations. I think that until the kext is signed legit this app needs a HUGE warning on it for Yosemite users. A cluttered and slow hard drive is better than a dead computer.

  3. Miguel Carvalho 2 years ago

    As one that actually bought the software, I can only support Doug. It does not make sense being hacking around good kernel drivers signing practices just to avoid a $99/yr license. Should i reclaim my money back?

  4. Jake Hanley 2 years ago

    Okay…..Seriously….Everyone need to REMOVE Trim Enabler until this is resolved.


    Because if anyone by accident should clear their pram, nvram etc. then they will surely become locked out of being able to boot into their system. It’s just NOT worth the gamble or frustration.

    Cindori – you need to get with Apple and get this licensed or certified or whatever you need to do at whatever cost to you. If you want your users to pay for it moving forward in order to help support your costs, then I’ll have skin in that game.

    At this point however, I personally have removed and uninstalled Trim Enabler (Sadly I might add) until you can provide us with a non-hacked version of your software.

    It is my opinion that you should NOT offer the software for download any longer until this is fixed. You are just aligning yourself for liability over other people’s data and OSX failures while you do still offer a hacked up ‘kext disabled’ version.

    Just my 2 cents…..I do hope that you get this resolved.


    • Author
      Oskar Groth 2 years ago

      This problem will not get fixed unless Apple changes their policy.
      Have you ever wondered why disk manufacturers like Corsair, Samsung etc. has never written a Trim driver for OS X? Or why they never offer firmware update software to OS X? (The only firmware updates they offer for Mac is a MS-DOS boot CD)

      The reason is that Apple is keeping the AHCI driver private, making it impossible for anyone, even these big companies, to create a driver for SSD’s.

      So the issue is not that Apple “doesn’t allow Trim Enabler”, but that they don’t allow anyone to create AHCI drivers.

      If they made public the AHCI driver, I would be able to make Trim Enabler “legit”.

    • highks 2 years ago

      Apple will never certify TRIM enabler, because Apple is actively blocking TRIM from working on 3rd party SSDs!
      They wrote extra lines of code to check for the SSD ID, and if it doesn’t say “AppleSSD” (or something like that) then TRIM will not be enabled.

      If they wanted TRIM to work on OSX for every SSD, they’d just have to remove that one line of code that checks for the Apple ID! But of course they won’t, because they chose to put it in there deliberately!

      So, trying to license a software that removes an ID-check that they deliberately put in their SATA drivers to make more money – that doesn’t sound like a very realistic endeavour, right?

  5. K 2 years ago

    Previous versions of Trim Enabler (Trim Enabler 3.2.x)
    Necessary because I want to use in OSX Snow leopard.

    Download (only the latest version, old is …) What Not?

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