USB4 and Thunderbolt: What the Tie Means

USB4 and Thunderbolt are now closely linked: USB4 is built on the Thunderbolt 3 protocol, and Thunderbolt 4 and Thunderbolt 5 are fully compatible with USB4. Practically, this means a single USB-C port can handle data, video, and power using either standard, and most modern laptops and devices will work interchangeably.

Background: Two Standards, One Port

Thunderbolt was developed by Intel and Apple, first appearing in 2011 on MacBook Pro models. It used a Mini DisplayPort connector and offered 10 Gbps data transfer. Thunderbolt 2 doubled that to 20 Gbps, and Thunderbolt 3 (2015) switched to the USB-C connector, which was a turning point. Meanwhile, USB (Universal Serial Bus) had its own evolution: USB 3.0 (2008) at 5 Gbps, USB 3.1 (2013) at 10 Gbps, and USB 3.2 (2017) at 20 Gbps. The USB Implementers Forum (USB-IF) wanted a single standard that could match Thunderbolt’s speed and features, so they based USB4 on the Thunderbolt 3 specification. Intel contributed the protocol royalty-free, which is why USB4 and Thunderbolt share so much.

How USB4 and Thunderbolt Work Together

Both standards use the USB-C connector and support the same core features: data transfer, video output, and power delivery. The key is that USB4 includes the Thunderbolt 3 protocol as an optional but widely implemented feature. This means a USB4 port can connect to a Thunderbolt device, and a Thunderbolt 4 port can connect to a USB4 device. The data transfer speeds are also similar: USB4 and Thunderbolt 4 both support 40 Gbps, while Thunderbolt 5 (released in 2023) goes up to 80 Gbps (and 120 Gbps in one direction with Bandwidth Boost). USB4 version 2.0 also supports up to 80 Gbps, so the two standards continue to evolve in parallel.

Key Differences: USB4 vs Thunderbolt 4 vs Thunderbolt 5

While they are compatible, there are differences in minimum requirements and certification:

• Thunderbolt 4 requires a minimum of 40 Gbps data transfer, support for two 4K displays, and PCIe data at 32 Gbps. It also mandates a minimum of one port that can charge a laptop.
• USB4 has a base speed of 20 Gbps, with 40 Gbps optional. Features like PCIe tunneling and DisplayPort are optional, so some USB4 devices may not support them.
• Thunderbolt 5 doubles the speed to 80 Gbps (or 120 Gbps one-way) and supports three 4K displays at 144 Hz or one 8K display. It is backward compatible with USB4 and Thunderbolt 3/4.

In practice, if you buy a Thunderbolt 4 device, you know it meets a high standard. A USB4 device might be slower or lack video output, depending on the manufacturer’s implementation.

How to Choose: USB4 or Thunderbolt?

When buying a laptop, dock, or cable, consider what you need:

• If you have Thunderbolt devices (like an external GPU or high-speed SSD), look for a Thunderbolt 4 or 5 port on your computer.
• If you just need a standard USB-C port for charging and basic data, USB4 is sufficient and often cheaper.
• For video editing or large file transfers, Thunderbolt 4 or 5 offers guaranteed high speeds and display support.
• Check the specs: a USB4 port may be 20 Gbps or 40 Gbps, so read the fine print.

Common Misconceptions

One common confusion is that USB4 and Thunderbolt are the same thing. They are not: USB4 is the base standard, and Thunderbolt adds extra requirements. Another misconception is that any USB-C cable supports Thunderbolt. In reality, Thunderbolt requires certified cables with specific electronics, and many USB-C cables are only USB 2.0 (480 Mbps). Also, just because a port looks like USB-C does not mean it supports USB4 or Thunderbolt; it could be USB 3.2 or even USB 2.0. Always check the port’s symbol: a lightning bolt icon indicates Thunderbolt, while a “SS” or “10” indicates USB 3.x.

Practical Impact on Devices and Peripherals

The unification means you can use a Thunderbolt dock with a USB4 laptop, or a USB4 SSD with a Thunderbolt 4 port, and it will work at the slower of the two speeds. For example, a USB4 20 Gbps device plugged into a Thunderbolt 4 port will run at 20 Gbps. Similarly, a Thunderbolt 3 device will work with USB4 and Thunderbolt 4 ports, but not with older USB 3.x ports. This compatibility is great for consumers, but it also means you should not assume maximum speed without checking both the port and the device. For instance, a USB4 cable might not support Thunderbolt 5’s 80 Gbps, so for future-proofing, look for Thunderbolt 5 certified cables.

Frequently Asked Questions

Is USB4 the same as Thunderbolt 4?

No. USB4 is based on Thunderbolt 3, but Thunderbolt 4 has stricter requirements (like 40 Gbps minimum and mandatory display support). A USB4 port may be 20 Gbps and lack video output, while Thunderbolt 4 guarantees 40 Gbps and dual 4K display support.

Can I plug a Thunderbolt device into a USB4 port?

Yes, if the USB4 port supports Thunderbolt 3 compatibility, which most do. The device will work, but at the speed of the slower standard. However, some USB4 ports (especially on budget laptops) may not support PCIe tunneling, so check the specs.

Do I need a special cable for Thunderbolt?

Yes. Thunderbolt requires a certified cable that includes the necessary electronics for high-speed data and video. A regular USB-C cable may not work or may limit speed. Look for the lightning bolt symbol on the cable or its packaging.

Will USB4 work with Thunderbolt 3 devices?

Yes, USB4 is designed to be backward compatible with Thunderbolt 3. A Thunderbolt 3 device (like an eGPU) will work with a USB4 port, provided the port supports Thunderbolt 3 tunneling.

Which is better for gaming: USB4 or Thunderbolt?

For external GPUs, Thunderbolt 4 or 5 is better because they guarantee PCIe data at 32 Gbps (or 64 Gbps for Thunderbolt 5), which is essential for GPU performance. USB4 might work, but if it lacks PCIe tunneling, it will not.

Is Thunderbolt 5 worth waiting for?

If you need 8K displays or very fast external storage, Thunderbolt 5 offers significant speed gains (80 Gbps). However, devices are still new and expensive. For most users, Thunderbolt 4 or USB4 40 Gbps is sufficient.

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