Before Yosemite, I was using a 3rd party app called Trim Enabler to turn on the TRIM command for SSD installed as an upgrade to HDD-based Mac. This is useful to prolong the life of older Macbooks. Yosemite new security model will no longer load the driver. The developer has released a new tool called Disk Sensei (https://www.cindori.org/safely-enable-trim-on-yosemite-and-el-capitan/). The new tool has more bells and whistles and doubled the price (US$19.99). Ouch! With the new version of Mac OS, a new, built-in solution is available. It's free. Under Mac OS X 10.10.4 or above, perform the following steps: 1) Launch Terminal 2) sudo trimforce enable 3) Confirm "yes" two times - Macbook will then reboot It is verified OS X El Capitan works with this function. 2016.10.07 - It is verified also that macOS Sierra final also works!
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