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Running a TB3 External Drive on a Late 2015 iMac....

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gpspad

macrumors 6502a
Original poster
Feb 4, 2014
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I am considering external drives, specifically a Samsung T5 SSD that's TB3/USB-C.

If I get a TB3-TB2 adapter, can I run this drive to my iMac?

Would I be better off just grabbing a Samsung EVO and throwing it in USB-3 enclosure, or even an old TB2 enclosure?

Are the TB3 ports enough of a reason to get a 2017 iMac vs a 2015? Researching external raid drives I can see the benefit of the TB3 ports, but I don't think I need one of those just yet.
 
Doesn't the late 2015 iMac come with USB 3 connectivity? Seems to me that this has been around for quite a while now. Samsung T5 drives come with two cables: one is is USB-C to USB-C and the other is a USB-C to USB- A (USB-3). No need for adapters if you have a USB-C or a USB-A port. USB-C is just the connectivity port, though, not the actual power behind it, and this is where confusion reigns. It is not the same as Thunderbolt 3. The T5 is not actually designed specifically for Thunderbolt 3, nor does it work at full Thunderbolt 3 speeds. It works with machines which have a USB-C port, though, including the 12" MacBook and the current lineup of MacBook Pros, etc. It also works with the USB-A (USB-3) ports on a 2015 Mac, and on 2015 MacBook Pros. I have been using T5 drives very happily with my machines since 2015. This past December I purchased a 2018 MacBook Pro and the T5 works just fine in it as well. MUCH faster than a 5400 rpm or 7200 rpm spinner drive!

One thing to realize, though, is that the T5 is NOT Thunderbolt 3. If you want that kind of speed you would need to purchase and use a Samsung X5, which is specifically Thunderbolt 3 and which works with the current line of Apple's machines with Thunderbolt 3 and a USB-C port. It is not useable on an older machine, though. I can easily plug in and use my T5 external SSDs on my older 2015 MacBook Pro and my 2017 MacBook, as well as the new 2018 MacBook Pro, but the new Samsung X5 Thunderbolt 3 external SSD that I recently purchased is only for use on my 2018 Thunderbolt 3 MacBook Pro. It will not work with an older machine. T5 will, though, and the speed is amazing. I have been thoroughly spoiled by these external SSDs!
 
Thanks I kind of forgot about the usb-c to usb-a adapter they include, I got hung up on the USB-C part.

In general does the TB3-TB2 allow you to use TB3 drives?

The more I look at things the more I think I would be better off getting a 2TB SSD and throwing it in a USB enclosure.
 
A T5 has a SATA III drive inside. USB 3 is about as fast as the drive inside. No need to try and hook it up to the TB port.

The X5 has an NVMe blade and yes, that should go through TB to get the most out of what you're paying for. TB3 to TB2 for that.
 
From what I understand, even if I were to plug in my X5 to my 2015's Thunderbolt port it would not work -- possibly it would with an adapter, but I am not interested in exploring that since I don't need to do so. It is NOT backwards-compatible. Used in an appropriate Thunderbolt 3 machine, yes, the X5 is fast, fast, FAST!!!! Faster than my beloved T5s. As Mike points out above, the T5 will plug into the USB-C port/Thunderbolt 3 on a current MacBook Pro or other machine which is similarly equipped but it will not work at the same speed as a device meant specifically for Thunderbolt 3 and appropriately set up to utilize the fast speeds. Nonetheless the T5 is still pretty darned fast in the 2018 MBP, faster than in my 2015 one, so no complaints here. For me, there is plenty of built-in flexibility with my current setup because I can use the X5 plugged into one Thunderbolt 3 port and one of my T5s plugged into another and quickly swap data around or add data to my heart's content. The X5 is not inexpensive -- whew! -- but it really IS worth it for certain uses and if one can afford it. These days I only use platter/spinner external drives for archival purposes, and for that they are just fine. Everything current I prefer SSDs, internal and external.
 
Clix Pix said:
From what I understand, even if I were to plug in my X5 to my 2015's Thunderbolt port it would not work -- possibly it would with an adapter, but I am not interested in exploring that since I don't need to do so. It is NOT backwards-compatible. Used in an appropriate Thunderbolt 3 machine, yes, the X5 is fast, fast, FAST!!!! Faster than my beloved T5s. As Mike points out above, the T5 will plug into the USB-C port/Thunderbolt 3 on a current MacBook Pro or other machine which is similarly equipped but it will not work at the same speed as a device meant specifically for Thunderbolt 3 and appropriately set up to utilize the fast speeds. Nonetheless the T5 is still pretty darned fast in the 2018 MBP, faster than in my 2015 one, so no complaints here. For me, there is plenty of built-in flexibility with my current setup because I can use the X5 plugged into one Thunderbolt 3 port and one of my T5s plugged into another and quickly swap data around or add data to my heart's content. The X5 is not inexpensive -- whew! -- but it really IS worth it for certain uses and if one can afford it. These days I only use platter/spinner external drives for archival purposes, and for that they are just fine. Everything current I prefer SSDs, internal and external.
Click to expand...
The X5 will work on a 2015 computer if you use the Thunderbolt 2 to 3 adapter. The adapter works in both directions.
 
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Ah...... Good to know! I don't have that adapter and probably wouldn't use it enough to bother with buying it, but I can see how for some it might be very useful. In my case usually the data that is going to be on the X5 is also going to be on at least one or two of my T5s anyway, so easy enough to do a simple transfer from the T5 to the X5 as needed.
 
In my case I think most cost effective would be to find a 2TB Drive for external storage. An SSD if I want speed and quiet, a regular HD if I just care about storage. SSD prices are dropping, what seems crazy now might be cheaper soon.

Ill then need a 6TB ((512GB+2TV)x2)drive to act as a TM backup for the iMac's SSD and the external drive.
 
Back in 2015 when I bought my 15" 2015 MB I had just a 512 GB SSD on it and knew that this would not be enough storage for me, either right off the bat or later on down the road. I was coming from a 2012 iMac with a 1 TB HDD (dog-slow 5400 one, at that). Anyway, I significantly pared down things before even going from the old machine to the new one and I also developed a strategy at that time of establishing a system of using "supplemental drives." These were and still are separate from my regular backups and I use{d) them to stash files and folders that I didn't really need on a daily basis but still needed to have conveniently at hand, rather than archived. Samsung's T* series of external SSDs were exactly what I needed then, starting with the T1, and what I continue to use today with the T5. I now have a new 2018 15" MBP and this has a 1 TB SSD, but even so I still prefer to offload extraneous stuff each month to a supplementary drive, and this system works well for me. I keep on the machine itself only what is necessary -- projects in progress, documents which need attention, etc. -- but everything else gets shifted off to a T5 SSD each month and this keeps the primary internal SSD on my computer "clean and lean," while anything I really need is still within reach very quickly by simply plugging in the T5. I just recently have added a Samsung X5 and am incorporating that into my overall setup; right now I am using it for photos, but may change that around after a while. The thing is so incredibly fast, it's mind-blowing! I love it! I want more of them for everything, but at this point in time, a bit too expensive for that..... As I did with the T* series I will add one more of these at a time over the next little while as prices drop and as I find the need......

I'd really love to be able to use a larger-capacity external SSD (5, 6, or more TB) for pulling together archived files, but that is going to be a while down the road, I think, both in terms of technology and pricing.
 
To use a bus-powered Thunderbolt 3 drive like the X5 with a Thunderbolt 2 Mac, you'll need both the Apple Thunderbolt 3 to 2 adapter (which doesn't supply power when connected to a Thunderbolt 2 Mac) and a power source for the drive like a Thunderbolt 3 dock:

https://support.apple.com/en-us/HT207266
"This adapter is bidirectional, which means you can use it to connect Thunderbolt 3 devices to a Mac that has a Thunderbolt or Thunderbolt 2 port. In that case, the Mac must be using macOS Sierra or later, and the device using Thunderbolt 3 (USB-C) must provide its own power."

Connect the Thunderbolt adapter to the Thunderbolt 2 Mac, then a Thunderbolt 3 cable from the adapter to one port on the Thunderbolt 3 dock, and connect the X5 to a second Thunderbolt 3 port on the dock for power. Something like this dock with two Thunderbolt 3 ports will work: https://www.amazon.com/Certified-Cable-Matters-Thunderbolt-DisplayPort/dp/B01DYFHYNS
 
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Thanks "astrorider" you just made me avoid a costly miss-step in thinking the TB3-TB2 adapter just did what I assumed it did, these things are much more complicated than just plugging dongle in.

Right now the late 2015 iMac I grabbed isn't looking so great, I didn't realize the lack of TB3 ports would be such a limitation in the future.

I was contemplating an older TB2 dock to add some more USB3 ports, but if I need to power any such devices a TB2 seems like a bad deal. I am better off going with a TB3-TB2 adapter and a TB3 dock?

No wonder everyone is getting rid of the TB2 docks.

I think I am going to look for a 2TB SSD powered via USB3 from the iMac; it won't be as fast but be the best I can do for the USB3 ports I have, the TB ports aren't going to be of much use for a single drive. Then maybe an older 6TB external TB2 drive to function as a TM Backup.
 
The T5 is pretty darned fast and I am sure it will be fast enough for your purposes; to me that makes more sense rather than trying to fool with the X5 which really is meant for use with Thunderbolt 3 devices, not older, less powerful machines. The X5 is bus-powered but it also contains its own heat sink, because it is capable of generating a lot of heat. The machine into which I am plugging it is also pretty powerful as well: 2018 MBP i9, Vega 20, 1 TB SSD storage. That is significantly more powerful than my 2015 15" MBP. My X5 has not gotten overly-warm, but then again I so far have not pushed it to a taxing degree. My T5s, too, get warm but again not excessively so. I sometimes plug in two T5s at the same time for the purpose of swapping or adding files, but I don't think I would do that with two X5s. I have used a T5 and the X5 both plugged in, and no problems there.
 
OP wrote:
"I am considering external drives, specifically a Samsung T5 SSD that's TB3/USB-C."

The above statement IS WRONG.
The t5 doesn't have anything to do with "thunderbolt".
It is a USB3 drive.
It comes with either a USB-c connecting cable, or a USB3 (type A) cable.

But again -- it has NOTHING to do with "thunderbolt".
For a 2015 iMac, you want to the use the cable with the USB3 (A type) connector and plug it into a USB3 port.
 
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