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I have an iMac from 2011, Mac OS X 10.6.8, and an SDD in a FW800/USB3 case. Which interface can let me enable TRIM: USB2, USB3, FW800 or Thunderbolt ?

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The interface you use to connect the external drive to your computer has no bearing on TRIM support and other ATA commands. Furthermore, your computer has neither USB 3 nor Thunderbolt. Hence, I've removed that segment of your question so your question is better-focused. – CajunLuke Mar 29 '12 at 19:07
@CajunLuke, the mid-2011 iMac should have Thunderbolt - it was part of the refresh, wasn't it? (see However, you're right - TRIM support doesn't depend on the interface. – JW8 Mar 29 '12 at 20:35
@JW8 Facepalm. For some reason I thought they'd been released this year, so I thought the 2011 models were too old. You're correct: the 2010 models wouldn't have TB, the 2011 models do. – CajunLuke Mar 29 '12 at 21:05
It's my question, I know better what I want to know so you don't edit it especially if you don't know what you're talking about. – user2113 Mar 29 '12 at 22:21

According to OS X Daily, TRIM is enabled for all Apple SSDs, but not for third party drives. The article claims that a third party utility, Trim Enabler, turns on TRIM for third party drives as well. More details can be found on the developer's page. Note that this utility isn't officially supported by Apple, so you should back up before installing the utility.

The interface of the external drive shouldn't matter for TRIM support (USB 2, FW800, or Thunderbolt). However, please note that Macs did not begin to natively support USB 3 until June 2012- with your 2011 iMac you'd be using USB 2 with one of those drives.

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Strictly speaking, it's not "effectively" USB 2, it is USB 2. – CajunLuke Mar 29 '12 at 19:09
@CajunLuke, indeed you are right. I meant to say that the USB 3 drive would be treated as a USB 2 drive - the drive can't take advantage of the benefits of USB 3. – JW8 Mar 29 '12 at 20:33
TRIM on OS X should not be enabled haphazardly. It has known issues with SandForce-based drives and may not be of any benefit with others. Apple does not enable it for a reason and it's not to sell more of their SSDs. – user10355 Mar 29 '12 at 20:36
The author of Trim enabler says that he doesn't think it could be enabled on an external SSD, that it depends on Apple - meaning that the interface DOES matter. – user2113 Mar 29 '12 at 22:25
@user2113, can you provide a reference to that? I don't see it... – JW8 Mar 29 '12 at 23:34

Yes, you can enable TRIM on an external SSD. I own a Lacie Rugged USB/Thunderbolt 128 GB drive and I enabled it with TRIM Enabler. I am using it as a boot drive.

I do not know if it is smart to enable TRIM but I could not find any posts where it would stand that TRIM can harm your external SSD.

But for any case, I have multiple backups of my SSD drive.

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Indeed you can, but it doesn't mean that the TRIM feature is used. – user2113 May 11 '13 at 12:52
Thanks, never thought about that. How can you find out if TRIM is used? – cahuk May 11 '13 at 19:30
I don't know, maybe by looking at how the data is stored, the sectors and blocks (I'm not familiar) – user2113 May 12 '13 at 8:15
I think that would do it, too. But did not find any appropriate scripts yet. – cahuk May 12 '13 at 11:04

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