iMac Pro Can a 2015 27" iMac boot from a Thunderbolt 3 external SSD?

[Turnpike]

I used a Samsung X5 which I believe is Thunderbolt 3 USB-C for a bootable external SSD for my 2017 iMac which went bad. From my research, even with adapters, I can't boot from it with my 2015's iMacs, is this correct?

It seems the iMac has Thunderbolt 2 and the Samsung X5 drive is Thunderbolt 3 and they can't work together? Just making sure, with those who understand this stuff. Thanks!

 

[PaulD-UK]

You can't connect the X5 directly to the Apple TB 2<>TB 3 adapter, as the adapter doesn't pass through the power the X5 needs to run.
You can get it to work by connecting the X5 to a powered TB 3 dock, and connecting the dock to the adapter, which is connected by TB 2 cable to the iMac.
This setup was bootable with older OSs. I don't know about current MacOS.
No cheap easy solution, I'm afraid.

 

[Fishrrman]

I'll offer a "cheaper, easier" solution:

This:

SAMSUNG T7 Shield 1TB, Portable SSD, up to 1050MB/s, USB 3.2 Gen2, Rugged, IP65 Rated, for Photographers, Content Creators and Gaming, External Solid State Drive (MU-PE1T0R/AM, 2022), Blue

Samsung T7 Shield Portable SSD delivers high performance on-the-go, not matter the terrain. It has an IP65 rating for water1 and dust2 resistance, with Dynamic Thermal Guard to manage heat control. Transfer huge files instantly. USB 3.2 Gen 2 and PCIe® NVMe achieve soaring sequential read/write ...

www.amazon.com

No, it's not going to -quite as fast- as a thunderbolt drive might be.
But it will still be pretty snappy once it's up-and-running.

 

[Juicy Box]

Yes, the Samsung X5 will work on older Macs with TB2 and TB3 ports. If I recall correctly, it requires at least High Sierra.

As someone already mentioned, Apple’s TB2/TB3 bi-directional adapter will not pass power over the bus, so you will need something to power it, such as a TB3 dock.

I used the X5 on my older Macs, as old as a Mid 2011 iMac. I tested the speed on a Late 2012 with TB1, and how read speeds as high as 900MBps.

I don’t have any TB2 Macs to test it, but suspect that speeds would be a little better on your iMac. Probably above 1400MBps.

All that said, the extra equipment and bidirectional adapter can be pretty expensive, even if you buy them used. Unless you already had some of it or planed on buying the equipment to use with a newer Mac some time later, it would probably be better to use a USB SSD.

 

[Turnpike]

Ok, my goal was to access the info on the TB3 drive, I don't mind putting stuff on a slower SSD going forward, so I can access it from all my machines here. So I'll start by looking at what kind of Thunderbolt docks there are out there.

Thanks!