Help - Booting w External SSD

F23

macrumors member
Original poster
Jan 4, 2014
98
30
Hi,

My 2011 iMac's hard drive has gotten so slow it's basically unusable. I have a 512 GB WD MyPassport SSD and have successfully used it to boot up the iMac and am running on it now. The external SSD uses a USB C port, but it came with a USB A adapter as well.

This is where I have an issue. The iMac has USB 2.0 ports, and I am getting 30 MBps read/write speeds. I got the Apple Thunderbolt 3 to Thunderbolt 2 adapter so I could connect the external SSD to the iMac using Thunderbolt instead of USB 2.0. But when I plug it in through Thunderbolt, the iMac won't recognize the external SSD at all. I tried restarting, ejecting, resetting NVRAM, nothing worked. I even tried plugging the external SSD with Thunderbolt to my 2014 Macbook Pro, it wouldn't recognize it either. I tried using another external SSD I have, with the same adapter and cable, it wouldn't recognize that one either.
Is there something I am missing here, with Thunderbolt connectivity or the adapter? Does it only work with USB? I've searched online but can't find anyone mention this issue. The external SSD won't even show up in Disk Utility through Thunderbolt. But when I unplug and use USB, it immediately recognizes it.

Any help would be appreciated,
Thanks.
 

cruisin

macrumors 6502a
Apr 1, 2014
956
215
Canada
USB C is not Thunderbolt 3, they just use the same plug. Thunderbolt 3 is essentially glued onto USB C using special chips for all of its features, and both devices need the chips otherwise it becomes USB C. So if you are trying to connect between the two there will be problems, as there is no easy way to convert from USB to Thunderbolt (or I haven't seen one). And the 2 to 3 Thunderbolt adapter is likely converting between Thunderbolt versions due to the cost savings.

If you look at the description for the Apple adapter:
The Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter lets you connect Thunderbolt and Thunderbolt 2 devices — such as external hard drives and Thunderbolt docks — to any of the Thunderbolt 3 (USB-C) ports on your MacBook Pro.

As a bidirectional adapter, it can also connect new Thunderbolt 3 devices to a Mac with a Thunderbolt or Thunderbolt 2 port and macOS Sierra.
So only between Thunderbolt.

And: https://community.wd.com/t/usb-c-to-thunderbolt-2/223571
 
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F23

macrumors member
Original poster
Jan 4, 2014
98
30
USB C is not Thunderbolt 3, they just use the same plug. Thunderbolt 3 is essentially glued onto USB C using special chips for all of its features, and both devices need the chips otherwise it becomes USB C. So if you are trying to connect between the two there will be problems, as there is no easy way to convert from USB to Thunderbolt (or I haven't seen one). And the 2 to 3 Thunderbolt adapter is likely converting between Thunderbolt versions due to the cost savings.

If you look at the description for the Apple adapter:

So only between Thunderbolt.

And: https://community.wd.com/t/usb-c-to-thunderbolt-2/223571
I understand now. thank you for the explanation.
 

J.Gallardo

macrumors 6502
Apr 4, 2017
266
54
Spain
Some people is still buying a LaCie portable external hard disk with Thunderbolt 2 interface for your purpose. I think the default version (an orange, rugged device; sorry, can't remember exact reference) uses a spin-drive which is very easy to replace with a 2.5 SSD, and this solution remains being the cheapest one I know for your use.
 
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