Thunderbolt vs USB-C: PORTending a Future of Unified Standards

If you’ve attempted to connect, well, pretty much anything to a computer in the last decade you’ve likely encountered the Thunderbolt™ vs USB-C conundrum. So what’s the difference between Thunderbolt and USB-C (or USB C, USBC, or USB Type-C depending on your favorite abbreviation)? And what’s the difference between the various Thunderbolt and USB generations?

What is Thunderbolt?

Thunderbolt is a type of hardware interface technology that’s used to connect peripheral devices (such as mobile phones, displays, T.V.s, and external hard drives, for example) to a computer. It is overseen by Intel, who co-developed the technology with Apple. You can read more about its interesting development here.

What is USB-C?

USB-C is the physical connector type used by both USB (Universal Serial Bus) and Thunderbolt to interface with computers and components. USB-C specifications are overseen by the USB Implementers Forum (USB-IF), a nonprofit organization created to promote and support the use of USB.

In the image below you can see four USB Type-A ports (the rectangular ports with the blue inserts), and two oval USB-C ports. Those USB-C ports support Thunderbolt, as indicated by the distinct lightning bolt logo between them.

Thunderbolt vs USB-C, what’s the difference? And do Thunderbolt docks work with USB-C?

The first thing to get out of the way is that “Thunderbolt” and “USB” are terms used to describe both physical ports and detailed technical protocols. A “Thunderbolt Port” is, in fact, a USB-C form factor port that’s used to connect devices via the Thunderbolt communication protocol. USB-C form factor ports are ALSO used to connect devices using the USB protocol.

In most cases, both Thunderbolt and USB-C cables can be used with Thunderbolt devices. Thunderbolt and USB protocols are both in their 4th generation and offer their own distinct capabilities. Check out the differences between USB-C vs Thunderbolt 4 in the chart below.

*The amount of power that a USB port can output is based on the USB Power Delivery (USB-PD) specification, which is completely separate from the USB generation and port type. At the time of writing, USB-PD is on version 3.1 and can provide up to 240W of power over compatible USB-C cables. Technically, USB-PD version 3.1 can be applied to USB 2.0, USB 3.X, and USB4 ports.

What is USB4?

USB4 is a technical specification released by the USB-IF in August of 2019. It followed the earlier versions of the USB standard, which we reviewed in length in a previous article. But here’s where things take one of many confusing turns. USB4 is based on the Thunderbolt 3 protocol specification, which Intel provided to the USB-IF. USB4 requires the exclusive use of the USB-C connector and the USB Power Delivery (USB-PD) specification.

Further expanding the confounding web of terms and versions, USB4 itself is on its second revision. For some light reading, you can immerse yourself in the full, 826 page USB4 v2.0 specification document, but the most notable change between the first and second versions of USB4 is a significant increase in the maximum data transfer rate. USB4 launched with a maximum data transfer rate of 40 Gbps. USB4 v2.0 provides support for 80Gbps bidirectional bandwidth, allowing for data to travel in either direction simultaneously at a maximum of 80Gbps.

The new standard also provides for an optional ability to send or receive data at up to 120Gbps when configured asymmetrically. The 120Gbps mode would employ three of the four available data lanes in a USB-C connection for upstream data while reserving the fourth 40 Gbps data lane for downstream data, hence the “asymmetrical” nomenclature. For a deeper dive into what asymmetrical configuration means, we’d recommend this article from Ars Technica.

What is Thunderbolt 4?

Thunderbolt 4 is the newest, commercially available version of Thunderbolt (as of the writing of this article). The Thunderbolt 4 specification was released by Intel in July, 2020. Although the announcement of Thunderbolt 5 was made in September of 2023, it isn’t expected to be commercially available until 2024.

As mentioned, Thunderbolt 4 also uses the USB-C port. Thunderbolt 4 has a minimum mandated data transfer speed of 32Gb/s. Mandating minimums in this way is what will, hopefully, lead to a clearer indication to users about the performance they can expect from their ports, cables, and peripherals. However, it’s important to note that device manufacturers are not required to support the maximum capabilities of Thunderbolt to earn their certification to use the Thunderbolt mark.

How do you know which USB or Thunderbolt version you have?

As you may have picked up on at this point, it’s one thing to understand how the various ports and generations of the standards differ, but it’s an entirely different challenge to easily understand what a given port can do when you plug a cable into it. Thunderbolt 4 and USB4 aim to at least try and make the lives of consumers easier. If users see a device labeled with the latest standard they can expect the minimum performance capabilities indicated in the table above.

To that end, in order for a device to earn the right to bear the Thunderbolt or USB4 marks, it must be certified by Intel or the USB-IF to meet the minimum capability requirements. A more stringent certification process is a step in the right direction, but the best way to make sure you understand exactly what your ports, cables, and destination devices are capable of in terms of data transfer speeds and power delivery is to consult your user’s manual.

Computers with Thunderbolt and USB4

The industrial computing space has an interesting relationship with modern connectivity standards. Many industrial systems still rely on technologies long since abandoned by the consumer computing world. For example, it’s still common to find serial ports (also referred to as COM ports), on industrial computers. On Industrial Computers, these serial connections frequently use the DB-9 variety of D-subminiature, or D-sub, connectors. Utilizing this type of connection ensures that both modern and legacy devices can be effectively connected.

That said, Thunderbolt 4 and USB4 connectivity is beginning to make its way into industrial computers, but adoption continues to be slower than the consumer space. Here at OnLogic, our Helix 401 and Helix 511 fanless computers both come equipped with Thunderbolt 4 certified ports. If you have questions about Thunderbolt vs USB-C or which systems support a specific connectivity standard, be sure to reach out to our team.

Note: This blog was originally posted on May 4th, 2023. It was updated for content on September 5th, 2023.