How to connect an external SSD to an 2015 iMac

Question

How to connect an external SSD to an 2015 iMac

Hi

After a fairly recent motherboard replacement in March by Apple, I am still getting differing speeds using an external SSD (via USB3). Last month it was checked again by a third party Apple approved repairer and they said it was a software fault. I am currently using Catalina and High Sierra on a dual boot, tested on both yesterday and an SSD usually with read and write speeds of approx 420Mbps each was down to 40Mbps on both OS.

The Crucial SSD I was using is just a few weeks old, and less than 50% full.

Options are:

1 - To plug the bus powered external SSD case directly into the back of my iMac

2 - Plug into a powered USB hub

3 - Plug into a powered external SSD / HDD dock and plug directly in to the back of my iMac

4 - No 3 but plugged into powered USB hub

Thanks

Matt

iMac 27", macOS 10.12

Posted on May 11, 2020 10:43 AM

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Answer 1

rkaufmann87

Level 10

143,712 points

May 11, 2020 11:41 AM in response to AppleMacCider

Well that is likely the problem it is BUS powered so the device is likely not getting enough power. If the enclosure cannot be upgraded to have an external power supply you will need to start over. One solution may be removing the SSD and putting the SSD in an enclosure that can have it's own power supply. One like: https://eshop.macsales.com/shop/owc-mercury-elite-pro-mini (NOTE: The enclosure does not come with the power supply so you will need to add one, OWC can help you get the correct one).

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Answer 2

May 11, 2020 1:08 PM in response to rkaufmann87

That would make sense. Being bus powered is causing the problem so connecting it to a powered USB hub won't help, it will need to be direct plug power to the SSD enclosure. I have checked OWC website and they are out of stock. Also, I am in the UK so will check out out OWC suppliers over here.

Thanks again

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Answer 3

May 12, 2020 12:00 AM in response to rkaufmann87

Thanks, have looked at a couple of websites and emailed for recommended OWC enclosure and plugged power cable.

Thanks for your help

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Answer 4

rkaufmann87

Level 10

143,712 points

May 11, 2020 11:07 AM in response to AppleMacCider

Please try the following:

Plug the SSD into it's own power supply and connect it's connection cable (I am assuming that is USB 3.0 or 3.1) directly to the back of the iMac. Then retest.

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