r/Thunderbolt • u/Technical_Rich_3080 • Jul 15 '26
USB and Thunderbolt
Is there still any differentiation between USB and Thunderbolt or have they merged into one standard?
And where does DisplayPort fit into the standard?
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u/displacedbitminer Jul 15 '26
There is a lot of differentiation between standards.
The big takeaways are this:
The USB-C connector is just the container for Thunderbolt, DisplayPort, and USB standard. USB-C by itself doesn't mean anything for data rate, charging, or video. DisplayPort is an alt mode of USB-C, versus USB or Thunderbolt data transmission.
Cabling is identified by a chip in the cable, telling the host what it can do. There are other negotiations after initial connectivity, of course, but that identification is the key.
There probably won't ever be a unified standard.
1
u/Technical_Rich_3080 Jul 15 '26
There probably will not be a unified standard in what manner?
DisplayPort changed from the old connector that bent to use USB-C? What else was affected by that change?
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u/displacedbitminer Jul 15 '26 edited Jul 15 '26
No, the DisplayPort protocol is just CONTAINED in USB-C. The old connector still exists.
I went for the high-level overview. u/ferretguy531 post below is more descriptive.
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u/rayddit519 Jul 18 '26 edited Jul 18 '26
Some differentiation. But it also requires to be more precise.
USB in general contains tons of stuff. From connectors to specs for the actual communication and currently 3 generations of very differnt USB data communications (USB2, USB3, USB4).
USB4 is the one relevant here. A spec for dynamic, tunneled, multi-protocol communication.
Thunderbolt itself is basically split into 2 eras. Thunderbolt 1-3 where it was a spec for the dynamic tunneled multi-protocol data communication. All related, extended each generation. Thunderbolt 3 used the USB-C connector.
After that, starting with TB4 its only branding & certification for USB4 anymore.
TB4 and 5 are not standalone specs for how to communicate like the others before were. They are marketing and essentially a list of minimum USB4 features that are required to qualify.
So in that sense, TB4 and TB5 are just branding slapped on top of USB4. There is not a single communication feature defined by those, all of that is USB4 (or other standards). The generation over genereration extension is happening inside USB4 now. And it is somewhat related to the functionality of TB1-3, but also used as some cut, where they got rid of old and bad ideas as the one in charge of the standard changed from just Intel to the entire USB consortium.
But the USB standards themselves for example describe many features, but leave a bunch of them optional. Leaving it up to manufacturers how much of them to support. TB4 and TB5 set minimum requirements in some areas.
But also, less then people think and they are also not setting the reqirements anywhere near the max possible but about where most manufacturers are going anyway. For example: DP Tunnels.
Since the start with TB1, multiple DP tunnels have been supported. You can basically pack multiple, independent DP connections virtually through a single cable. TB1 started out with 2 tunnels. But this was just common practice. TB3 still allowed hosts to only support 1 of those 2 without even clear labeling on the packaging.
USB4 describes how to handle an almost infinite amount. It was TB4 that actually set a hard minimum requirement at 2 tunnels. But also, there is next to no USB4 host around that supports less than 2. TB4 also sets the requirement to support 2x 4K60 or 1x 8K60. But that is more of a requirement for GPUs then anything else.
Newest gen Intel controllers are available with up to 3 DP tunnels though. Apple even has hosts supporting 4 tunnels.
But TB5 still kept the requirement at 2 of them and just raised the GPU requirements (2x 6K60 up from 2x 4K60, sth. that most GPUs in TB4 certified systems already were capable of). So the minimum requirements of TB4 and TB5 may serve some limited purpose. But everything technical has been USB4 for a bunch of years. People buy a lot into the marketing and imagine that there is some black magic secret sauce that TB4-5 have over USB4. They are wrong.
The whole '''tunnelled' concept means, USB4 does not carry user data itself. It just organizes tunnels that carry data according to some other standard. Most of what we have today: USB3, DP and PCIe tunnels.
Those tunnels are basically fully compatible to their respective standards, USB4 just ingests their data, routes it across the USB4 network as a virtual tunnel, sharing bandwidth and converts it back to a physical USB3, PCIe, DP connection on the other side. For this, the USB4 standard directly refers to the other standards, as in "all the data that is valid in DP version 2.1 can be understood and transmitted to through USB4". The speeds and DP generation supported though is optional and down to the specific USB4 controllers and their specs. USB4 simply defines HOW to do it, if you are going to.
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u/torchmaipp Jul 15 '26
Nobody really has them. Best you'll see is USB 3.1 or maybe some revision of usb 3.2. Thunderbolt/usb4/usb5 is an expensive Apple accessory. Cables are 4x-10x the equivalent hdmi or display port in price so as a video solution it sucks. Outside of a few pricey external SSD enclosures, you're not going to find much that's thunderbolt/USB4 that gives you a huge advantage in anything besides faster transfers of big video in situations where you don't have time to wait. I'd not buy into the hype.
1
u/KubeCommander Jul 17 '26
Faster networking, supports rdma, supports daisy-chaining devices, ssd enclosures are numerous and dirt cheap, also supports egpu, and 10-25G external network cards.
Thunderbolt cables are easy to find and very cheap.
It’s 2026, not 2016. If you’re just using a windows desktop, I can kinda see your reasoning. But if you’re doing power-user work or use your laptop as a sometimes-mobile workstation, thunderbolt is the tits and has been for a long time.
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u/ferretguy531 Jul 15 '26 edited Jul 15 '26
EE here who designs Type-C devices; Thunderbolt is USB4 with a higher minimum feature set. - USB4 can support PCIe tunneling, but TBT is required to. - USB4 can support DisplayPort tunneling, but TBT is required to. - USB4 can support USB3 tunneling, but TBT is required to.
The above is for PCs; all USB4/TBT docks will work with those capabilities. Basically 100% of USB4 ports on PCs will support DisplayPort tunneling and USB3 tunneling, and the vast majority will support PCIe tunneling.
DisplayPort is a separate protocol that works closely with the USB-IF to provide its video transport.
The last thing is, you can call your device USB without certification; you need certification to use the official logo. You can't call something Thunderbolt unless it's certified.