USB-C, Thunderbolt 3, Thunderbolt 4, and USB 4

Updated 3 months ago by Emma Stone

What are USB-C, Thunderbolt 3, Thunderbolt 4, and USB 4?

USB-C is a connection type. USB-C is not Thunderbolt 3, Thunderbolt 4, or USB4. It is just the connection that those technologies use. To understand the difference between each of the aforementioned technologies, you have to look beyond the USB-C connector that each solution uses to plug in.

Graphic showing Thunderbolt 4, Thunderbolt 3, USB-C and USB4 ports

What is the difference between Thunderbolt 3, Thunderbolt 4, and USB 4?

Thunderbolt 4 guarantees certain specifications that are optional with the Thunderbolt 3 standard. Thunderbolt 4 is always 40 Gigabits per second, while Thunderbolt 3 and USB 4 can operate at either 20 or 40 Gigabits per second.

The difference between Thunderbolt 3 and USB 4 is mostly in the name. The actual standards are very similar, though there are some exceptions like signal frequency. For example, Thunderbolt 4 is 10.3125/20.625 Gbps while USB4 is 10/20 Gbps.

With Thunderbolt 3, PC users were often limited in features, whereas Apple provided full Thunderbolt 3 feature set support. PC users regularly lacked the full 40 Gbps, couldn’t support multiple displays or deliver power. Fortunately, with today’s Thunderbolt 4 standardization and certification, PC users get the full feature stack that Apple users got with Thunderbolt 3.

New Thunderbolt 4 features

Thunderbolt 4 does add some new features, too (both host and device-based), such as:

Host

  • Where Thunderbolt 3 was required to support only one external 4K monitor, now every Thunderbolt 4 laptop has to support up to two 4K displays or one 8K display.
  • Thunderbolt 4 now ensures that you can wake a computer with the shake of a mouse or the tap of a keyboard on Thunderbolt 4 docks. This wasn’t always the case with Thunderbolt 3.
  • Thunderbolt 4 is also a more data-safe technology, as it requires Intel VT-d-based direct memory access (DMA) protection, also known as DMA remapping.
  • Thunderbolt 4 requires storage speeds up to 3,000MBps, which is double the minimum requirements of Thunderbolt 3. With Thunderbolt 4, you will have all four lanes of PCI Express available – so PCIe can use up to 32Gbps of the total 40Gbps Thunderbolt bandwidth. With Thunderbolt 3, depending on your laptop manufacturer and model, some would only see 16Gbps of PCIe bandwidth.

Cable + Device

  • Another advantage of Thunderbolt 4 is that cables can be up to 2 meters long and still handle 40Gbps bandwidth and DisplayPort capability. Previously, passive Thunderbolt 3 cables had to be less than 1 meter to handle full bandwidth and support DisplayPort.

Device

  • You’ve always been able to “daisy chain” Thunderbolt devices, but with Thunderbolt 4 hubbing, you can now have up to four Thunderbolt ports in a hub or dock – each in a separate “branch” that can be disconnected without affecting any of the other Thunderbolt devices connected in other ports.

Summary of the Main Differences

Thunderbolt 4

Thunderbolt 3

USB4

USB3

Signal Bit Rate

10.3125G/20.625G/10G/20G

10.3125G/20.625G

10G/20G

10G

One Universal Computer Port

Yes

Yes

 X

 X

Universal 40Gbps cable (up to 2 meters in length)

Yes

No> 0.7 m requires active cable[1] 

 X

 X

Up to 4 ports for Hubbing

Yes

 X

 Yes

 X

Speed (Host Min. Requirement)

40Gbps

20Gbps

20Gbps

10Gbs

Video – up to

2x 4k display or 1x8k (@60Hz)

1x 4k display

1x 4k display

1x 4k display

Data – up to

PCIe (32 Gbps)USB 3.2 (10Gbps)

PCIe (16 Gbps)USB 3.2 (10 Gbps)

USB 3.2 (10 Gbps)

USB 3.2 (5 Gbps)

PC Charging on at least 1 computer

Yes

 X

 X

 X

PC Wake from Sleep

Yes

 X

 X

 X

Minimum Port Power for Accessories

15W

15W

7.5W

4.5W

Thunderbolt Networking

Yes

Yes

 X

 X

Mandatory certification for shipping computers, cables and accessories

Yes

Yes

 X

 X

Cable testing audits

Yes

Yes

 X

 X

Intel VT-d based DMA protection

Yes

 X

 X

 X

USB 4 Specification

Compliant

Compatible

Compliant

Compatible

Notes:

  1. Thunderbolt 3 cables longer than 0.7 meters are active cables which do not support DisplayPort
  2. There are different Thunderbolt 3 cable types – 20Gbps, 40Gbps, Active, Passive, 60W, 100W
    • Less than 1 meter: Passive, 40Gb TB3, USB 10Gb, DisplayPort, works with USB-C display directly
    • 1 meter and greater:
      • Passive: 20Gbps TB3, USB 10Gb, DisplayPort, works with USB-C display directly
      • Active: 40Gbps TB3, USB 480Mb, DisplayPort, DOES NOT work with USB-C display directly
  3. DisplayPort differences
    • Thunderbolt 4 – DisplayPort 1.4 (HBR3) supported up to 2 meters with passive cables
    • Thunderbolt 3 – DisplayPort supported with passive cables (less than 1 meter) but active cables (1 meter or greater) do not carry DisplayPort signal and won’t work to drive a USB-C display

Connecting Thunderbolt 3 Devices with Thunderbolt 4 Cables or vice versa

Thunderbolt 3 capable devices can be interconnected using a Thunderbolt 4 cable. Since Thunderbolt cables are backward compatible, users can expect Thunderbolt 3 performance from this connection.

But what happens when you use a Thunderbolt 3 cable to connect a Thunderbolt 4 Hub/Dock to a host? 

In some instances, and depending on the devices being connected, you may not see any issues at all. Some specifications that were optional with Thunderbolt 3 are now guaranteed to work with Thunderbolt 4 – so your device may or may not work with a Thunderbolt 3 cable. Or in other instances—for example with active cables longer than 1 meter—you will see display issues and may not have full Thunderbolt 4 feature support.

Regardless of whether the device is USB 4, Thunderbolt 3, or Thunderbolt 4, it’s best to purchase a Thunderbolt 4 cable to guarantee full compatibility.

What should you buy?

Contact TechNosis to make sure you are purchasing the correct cables for your needs.


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