What I learned in almost ten years supporting Plugable Thunderbolt Docking Stations

In May of 2017 Plugable launched our first Thunderbolt 3 docking station, the TBT3-UD1-83, and to coincide with that launch I made a video demonstrating its features and capabilities.

In the almost ten years since that initial TBT3-UD1-83 product launch Plugable has introduced a number of industry leading Thunderbolt 3, Thunderbolt 4, and Thunderbolt 5 docking station products (such as the TBT3-UDZ, TBT4-UDZ, and TBT-UDH2) and since day one I have been part of the Plugable team supporting those products.

Suffice to say, after almost a decade of helping our customers I have learned a great deal about what factors can cause unexpected behavior when using a Thunderbolt docking station. In this blog post I wanted to share what I have learned, and what to check if things are not working as expected.

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When it comes to a Thunderbolt docking station, the cable being used to connect the dock to the host computer plays a very important role. If the cable is not up to the task, then there will be problems.

To put it simply, a Thunderbolt cable carries an extraordinary amount of information at a very high speed. In addition, Thunderbolt cables support a standard called USB Power Delivery (aka USB-PD), which is what allows a Thunderbolt docking station to charge the host computer at a specified rate.

If the cable in use does not support the appropriate specification, standard or USB PD charging rate, the result will be:

• Information will not transfer at the expected rate
• The monitors connected to the dock may not work at the desired resolution or refresh rate, blink on and off, or may not work at all
• The computer may not charge at the expected rate, or not at all

When it comes to Plugable Thunderbolt docking station products, Plugable always includes in the box a Thunderbolt cable that has been certified by Intel to meet the appropriate specification and meets or exceeds the maximum USB Power Delivery charging rate offered by the docking station model.

All Thunderbolt cables included in the box with a Plugable Thunderbolt docking station are labeled with both the docking station model number and the cable’s specifications, in order to help make them easier to identify as well as verify their specifications.

For example, the cable included with the Plugable TBT-UDH2 Thunderbolt 5 Dual HDMI display docking station has a label that on one side says:

“plugable.com/tbt-udh2” (which provides both a link to the product page as well as the model number)

And on the opposite side says:

“Thunderbolt™ 5 (80/120Gbps) USB-C 240W, DP 2.1, 3.3ft/1m” (which provides the cable’s specifications)

Using the example above, let’s break down each piece of information:

Thunderbolt 5

‘Thunderbolt 5’ refers to the specific Thunderbolt standard the cable is designed and certified to support.

Note, Thunderbolt 5 cables are backwards compatible with Thunderbolt 4 and Thunderbolt 3 devices.

80/120Gbps

‘80/120Gbps’ refers to the amount of information bandwidth provided by the cable, as set by the Thunderbolt 5 standard.

Under normal circumstances when information is being sent bi-directionally between the host computer and the docking station in a symmetrical fashion, the cable provides 80 Gigabits per second of information bandwidth.

When a Thunderbolt 5 host computer enables ‘Bandwidth Boost’ mode (which provides additional bandwidth for higher video resolutions and refresh rates), the cable supports 120 Gigabits per second of information bandwidth from the host computer to the docking station, and 40 Gigabits per second of information bandwidth from the docking station to the host computer in an asymmetrical fashion.

USB-C 240W

‘USB-C’ refers to both the connector type and the standard being referenced, which in this case is the USB Power Delivery standard. ‘240W’ indicates that the cable is rated to carry up to 240 watts of power from the docking station to the host computer.

DP 2.1

‘DP 2.1’ indicates that the cable supports transporting a video signal that supports the DisplayPort 2.1 specification.

So what does all of this mean when it comes to practical use and troubleshooting?

Host system specifications

When it comes to determining a computer’s compatibility with a Thunderbolt docking station, it is important to verify the computer’s specifications. If the host computer’s specifications do not meet the minimum requirements of the docking station, then things may not work as expected.

When it comes to specifications, the primary factor is whether or not the host computer has Thunderbolt support built-in, and if so, which version of the Thunderbolt specification is supported.

For reference, the Thunderbolt standard has seen three revisions over the past decade. Thunderbolt 3 was introduced in 2015, Thunderbolt 4 was introduced in 2020, and Thunderbolt 5 was introduced in 2023.

Speaking in general, Thunderbolt 5 host computers are compatible with Thunderbolt 5, Thunderbolt 4, and Thunderbolt 3 devices. In other words, computers supporting the latest Thunderbolt standard can support devices from previous Thunderbolt generations that use a USB-C connector.

However, it is important to note that the opposite is not always true. For example, a computer with Thunderbolt 3 support will typically not be compatible with a Thunderbolt 5 docking station.

Why? Because Thunderbolt devices based on the latest version of the specification often require the host computer to have a version of Thunderbolt that meets or exceeds the Thunderbolt version of the device in order to work properly.

Note, previously I said, ‘often’, which implies that there can be exceptions.

Thunderbolt 5 Dock

For example, the Plugable TBT-UDH2 docking station is a Thunderbolt 5 docking station. This means that a computer must have Thunderbolt 5 support built-in in order to make full use of the docking station’s capabilities.

View the TBT-UDH2

However, Thunderbolt 5 docking stations are backward compatible with Thunderbolt 4 computers. The limitation is that some of the advanced features of the Thunderbolt 5 docking station will not be enabled when the docking station is used with a Thunderbolt 4 computer.

So what have we learned?

When it comes to determining compatibility with a Thunderbolt docking station, an important step is determining if your computer supports Thunderbolt, and if so, which specific version. In general the version of Thunderbolt support built into the computer should meet or exceed the version of Thunderbolt used in the docking station, however there are exceptions when it comes to using Thunderbolt 5 devices with Thunderbolt 4 computers (at the cost of somewhat reduced performance).

Device firmware updates

For reference, the term ‘firmware’ generally refers to software that controls how computing hardware operates at a low level.

Thunderbolt computers and Thunderbolt docking stations both have inside of them ‘Thunderbolt NVM’ firmware. To put it simply, the Thunderbolt NVM firmware governs how the devices communicate with each other, and how they operate together. As each version of the Thunderbolt specification has matured, so has the NVM firmware.

When Thunderbolt 3 was initially introduced in 2015, it was a revolutionary upgrade as compared to the previous versions Thunderbolt 2 and Thunderbolt (also known as Thunderbolt 1).

Since the technology was so new and constantly evolving, many computer manufacturers were consistently publishing Thunderbolt NVM firmware updates for their systems that improved both compatibility and performance.

When Thunderbolt 4 was introduced in 2020, it was more of an evolutionary upgrade as compared to Thunderbolt 3. While Thunderbolt NVM firmware updates were still being provided as Thunderbolt 4 systems permeated the market, the cadence was not as frequent as compared to Thunderbolt 3. Further to this, Thunderbolt technology was often being integrated within the host computer’s CPU. This meant standalone NVM firmware updates weren’t required, and updates to the NVM firmware were often included with System BIOS updates (more on that later).

System BIOS / UEFI firmware updates (Windows)

Windows computers typically have what is known as a ‘System BIOS’ or ‘UEFI firmware’ within them. The details behind both terms are technically very different, however for the purposes of our discussion we can refer to both as the ‘master’ firmware that controls how the computer operates at a low level.

The System BIOS / UEFI firmware version can have an impact on the compatibility and performance of a Thunderbolt docking station. As mentioned previously, many modern Windows computers have Thunderbolt support built into the host system’s CPU. As a result, when using a Windows computer it is important to ensure that the computer has the latest System BIOS / UEFI firmware installed in order to ensure the best overall compatibility and performance.

For reference, Mac computers will update their UEFI firmware automatically as a result of standard macOS updates.

Graphics Processing Unit (GPU) drivers

While there can be exceptions, speaking in general most Thunderbolt docking stations rely on the host system’s internal graphics processing unit (GPU) in order to drive the dock-connected displays. As a result, the driver for the host system’s GPU can affect the compatibility and performance of the connected displays, so it is important that the latest GPU drivers are installed. macOS handles GPU driver updates automatically, so this detail is only applicable to Windows systems.

概要

In summary, the key details when it comes to making sure a Thunderbolt docking station will work as expected with your computer are:

Frequently asked questions