Cindori used to make Trim Enabler as a free piece of software but as the mac OS has developed the needs for Trim software have changed. Trim Enabler is now $9.99 from Cindori.

Why Is TRIM So Important?

When the OS, (Mac, Windows or Linux) uses TRIM with a solid-state drive, it sends a signal to the SSD every time you delete a file. The SSD then knows that the file is deleted and it can erase the file’s data from its flash storage.  Nothing special there then, after all that is how rotational drives work. They don't actually delete the file, they tell the system that the space that was occupied by the 'deleted' file is now available for reuse and so can be overwritten. Unerase type apps depend on this fact so that if you should delete a file in error you should resolve that asap. The longer you leave it the less likely it will be possible to recover the file.With flash memory, it’s actually faster to write to empty memory than to write to full memory, which means that the memory should first be erased and then written to. This causes your SSD to slow down over time unless TRIM is enabled. TRIM ensures the physical NAND memory locations containing deleted files are erased before you need to write to them. The SSD can then manage its available storage more intelligently.  

What About Garbage Collection?

There is also some debate as to whether Garbage Collection on its own is sufficient to keep an SSD drive in tip top condition. So I asked Crucial about whether I could or should use the TRIM function on my M4 drive. This was their response...

I do not normally recommend enabling the Force Trim command, as this can potentially corrupt or damage data being stored on the drive.  As the M4 has built-in garbage collection, TRIM is not necessary for the drive to maintain performance.  In order to activate the built-in clean up, all you need to do is restart the computer while holding down the 'Options' key.  This brings you to the Boot Manager screen, where you will leave the system for a period of 6-8 hours (typically overnight is the recommended time).  This procedure gives the drive idle power, which allows the controller to activate the Active Garbage Collection.  The Garbage Collection will clean up any invalid data being stored on the drive.  This sequence should only need to be done once every 2-3 months, depending on usage and writes performed on the drive.

Proceed With Caution

Apparently, not all TRIM commands are the same. Different SSD drives have different protocols for the TRIM function. What this can mean is that if you enable the TRIM function on Mac OS 10.10 and above, it can only issue the Apple protocol for the TRIM command. Other brands may misinterpret this command and delete wanted data rather than unwanted data. The consequences of this can be huge data loss.

So my advice to all Mac users is to think very carefully before enabling the Force Trim command unless you have either an Apple or Angelbird SSD drive. I have bought an Angelbird SSD drive for my Mac Pro Cheesegrater.