Thunderbolt 3 only works at USB2.0 speed with Samsung T5 ssd

First, just for clarity, Thunderbolt 3 and its software wouldn’t come into play here because the Samsung T5 isn’t an actual Thunderbolt device and therefore wouldn’t interface with the Thunderbolt controller chip. It’s a USB 3.1 device, and even though you can connect it to a USB-C/TB3 port (as you can with any USB device), it will still only ever work as a USB device. If it were an actual Thunderbolt device (like the Samsung X5), then it would ONLY work over Thunderbolt and would not operate over USB at all, at least until Intel’s new backward-compatible Thunderbolt controllers find their way into products.

In terms of the issue, are you using the USB-C to USB-C cable that actually came with the T5? The reason i ask is that if you aren’t, not all USB-C cables are created equal. Some of them only support carrying USB 2.0 data. Others only support USB 3.1 Gen 1 (5 Gbps), whereas the T5 can use USB 3.1 Gen 2 when plugged into a suitable port using a suitable cable. I wrote a detailed post about the variety of USB-C and TB3 cables here if you’re curious: https://www.dell.com/community/Laptops-General-Read-Only/Demystifying-USB-C-cables-one-connector-VASTLY-different/td-p/5153422

Thanks a lot for your reply. I agree T5 is not a thunderbolt device, but it should be able to work as USB3.1 in that USB-c/TB3 port. So I am not sure if this is normal.

As for the cable, I am using the USB-c to USB-c cable that came with T5.

Ok, then the next step would be to try to isolate variables here to identify the cause of the problem. Since the T5 is confirmed to run at USB 3.0 speeds when connected to the system’s USB-A port, the remaining culprits are the system’s USB-C/TB3 port and the cable you’re using. So I would run either of these tests to figure out which it is:

- Connect a different device that supports USB 3.x to the USB-C/TB3 port. If all of your other USB 3.x devices use regular USB-A, you’d need to use a USB-A cable plus a USB-C to USB-A dongle to plug that device into the USB-C port. (Note: The dongle might limit speeds to 3.1 Gen 1 rather than Gen 2, FYI.) 

- Try a different USB-C to USB-C cable with the T5. Make sure it’s rated to support at least USB 3.1 Gen 1, although the T5 will use Gen 2 if available, but USB-C cables that support that are less common.

Also, I suppose just for good measure you could see if there are any firmware/BIOS updates for your system and also for the T5 in case there’s some issue specifically between that system and the T5 or the T5 specifically when connected via USB-C.

I have updated to the latest BIOS and firmware for both the laptop and ssd and did several tests per your suggestion.

I tried another WD passport ssd. It still works at USB2.0.

Also I tried a USB3.1 dungle from USB C to USB A. It still works at USB2.0.

The last thing I tried is to get a thunderbolt 3 supported cable. This time it can work at USB3.1.

So I guess the thunderbolt 3 port cannot work with USB3.1 usb c cable. This might be a bug.

I’m glad it’s working, but that is very strange. What system model do you have? I just realized you never mentioned that. Anyway, that does sound like a bug somewhere, especially if the USB-C cable that came with the SSD isn’t working. A regular (passive) Thunderbolt 3 cable when used with regular USB works just the same as a USB-C cable that supports at least USB 3.1 Gen 1 (maybe Gen 2 in some cases, not sure), but an ACTIVE Thunderbolt 3 cable only supports USB 2.0 when used as a regular USB cable.

Did you try your T5 and the cable that came with it on another system, or is this the only one you have with USB-C? And just to make sure, when you tried the dongle, what exactly did you do? Dongle plugged into the USB-C port and then a USB-A cable from the SSD to the dongle? If so, did you make sure that the USB-A cable you tested with works with USB 3?

Again, I’m glad it works, but I wish I understood why using a Thunderbolt 3 cable is necessary, because it shouldn’t be, in fact it should work completely identically to a USB-C cable in that situation. Strange....

Interesting mention about the loose connector.  On a USB-C connector, the USB 3.1 pins are toward the edges of the connector and the dedicated USB 2.0 pins are near the center, so theoretically I suppose a cable that was skewed in the connector might cause the USB 3.1 pins to fail to connect.  But I admit I personally haven't seen any reports of that issue.  And if that was the cause, I'm not sure why the Thunderbolt 3 cable would work properly unless it just happens to be slightly larger than both the regular USB-C cable and the dongle so that it fits more securely in the connector.  But that seems like a long shot.

I am using a Latitude 7480. The ssd works fine with a macbook pro of my friend's. I did use a USB3.1 supported dongle and type A cable for the test.

Anyway, I couldn't figure this out. Maybe hardware issue. One thing I noticed is that the type c port on 7480 is pretty loose. Sometimes a minor shift of the device may cause disconnection. Not sure if this is related.

---

@MD7480 wrote:

Problem solved. I contacted Dell support and they sent an engineer to help replace the port.Now it's working fine. The engineer said they've actually met a lot connection issue related to type c port. The port is just too thin and not durable. Hopefully there will be a hardware improvement in future generation ports.

---

Interesting!  Glad to hear it's working, although sorry you had to deal with a hardware replacement.  The TB3/USB-C port is an industry standard, so I don't know how much flexibility Dell has at when it comes to reinforcement, but if there is something they can do, then I certainly agree that I hope they do it, especially if these issues aren't experienced on the TB3/USB-C ports of systems made by other vendors.

My apologies for the super rookie question, but what program are you using to test the current and max speed of your functioning devices?

what software did you use to check the usb info?

Dell supports assist used to have that function, but I cannot open it since the latest update.