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HDG Explains : What is Thunderbolt?

In the “good old” days of personal computers, each peripheral seemed to need its own connection standard. In the end, we were lucky with USB, but its versatility was disappointed by its relatively slow speed, low power consumption, and confusing array of connectors

What is Thunderbolt? Thunderbolt is a computer peripheral interface that provides the most elegant all-in-one solution for connecting devices to a computer. Thunderbolt 3 is currently the latest version of Thunderbolt, and by the end of this article, you’ll know everything you need to know to use this fantastic new connectivity standard.


The history of Thunderbolt in a flash

Thunderbolt is the result of a collaboration between Intel Corporation and Apple Computers. Since Apple computers have traditionally been used by creative professionals, they always needed a high-speed peripheral connection. For years, Apple’s answer to this was FireWire, but over time, the limitations of FireWire began to show.

Intel and Apple collaborated on a standard that was originally codenamed “Light Peak“, hinting that this new interface was designed to use optical cables.

not copper wire. In addition to high bandwidth, optical cables are promising because of how long cables can be without signal loss.


While optical Thunderbolt cables are actually available today, most cables are traditional copper, so there are quite stringent length restrictions for Thunderbolt cables today.

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The first Light Peak laptop was demonstrated in 2010 using optical technology, but copper is the norm to this day. This has the great advantage that copper wiring can also carry power.

The name “Thunderbolt” was first revealed to the world in 2011, when the technology was added to the MacBook Pro line of that year. The same year, the first Thunderbolt ports appeared on the iMac. Thunderbolt 2 debuted in 2013, doubling the speed of the first generation. The current Thunderbolt 3 standard received hardware support in late 2015 as part of the Intel Skylake generation processors.

Go lightning creamed! Thunderbolt specs in a nutshell

Thunderbolt is actually a combination of two other existing protocols. The first is PCI Express. This is the same communication standard that your GPU uses to send and receive information. As you probably know, GPUs require a lot of bandwidth, making this protocol an excellent protocol for connecting almost any peripheral device.


The first generation of Thunderbolt connections can send data at 10 Gbps and at the same time receive data at 10 Gbps. It has a 10 Gbps dedicated channel in any direction. Compare that to USB 3.2 Gen 1, which only delivers half that speed.

Thunderbolt 2 has doubled the available speed to 20 Gbps, while Thunderbolt 3 offers a whopping 40 Gbps. USB 3.2 2×2 reaches a maximum speed of 20Gbps. That’s still half of Thunderbolt 3. With so much bandwidth, it opens up all sorts of innovative applications, which we’ll detail below.

Backward compatibility with Thunderbolt 3

It’s important to remember that Thunderbolt and physical connectors are actually two different things. Although Thunderbolt 1 and 2 use a connector based on the DisplayPort standard, they are actually Thunderbolt 3 compatible if you’re willing to shell out some money for an adapter. As you would expect, these devices cannot operate at higher speeds than they were designed.


Since all Thunderbolt 3 ports also include a USB controller, you can plug any USB device into the Thunderbolt port and it will work fine. However, devices using Thunderbolt 3 exclusively will not work with a USB-C only port, despite having the same physical connector.

Likewise, you must use a Thunderbolt 3 cable to take advantage of the bandwidth and functionality of Thunderbolt 3.

Thunderbolt 3 and USB-C telling regardless

Thunderbolt 1 and 2 use a special port based on the DisplayPort design, so they should never be confused with USB. However, Thunderbolt 3 controllers and USB-C controllers use the same port. The only real way to tell them apart is to look for the markings.


For example, a MacBook has a small lightning bolt icon next to the port in question. Likewise, Thunderbolt 3 cables are usually marked with the word Thunderbolt or a small lightning bolt. Of course, there is no risk if you just plug in the device to see if it works or not.

How is Thunderbolt 3 used

Thunderbolt 3 is becoming quite popular in laptops, especially when it comes to ultrabooks. Apple has fully adopted Thunderbolt 3 in its latest MacBook lineup. You won’t find other ports on a modern MacBook. Even charging is provided on the Thunderbolt 3 ports.

As mentioned above, Thunderbolt 3 can be used in a hub and spoke topology or in a daisy chain. If you only have Thunderbolt 3 devices, you can connect the first to a port, then to that device, and so on. This means that having a small number of ports is not a problem.


The reality is that most of the peripherals you find are not Thunderbolt 3 devices. This means purchasing a Thunderbolt 3 (or USB-C) hub is the only practical way to connect typical components to your computer.

It’s actually quite handy when it comes to a desktop docking station. You can connect all of your desktop peripherals to the hub. When you get to your desk, you only need to connect one cable to the machine to turn it into a full-fledged desktop computer, as well as charge the laptop.

With the huge available Thunderbolt 3 bandwidth and native PCIe support, we can now connect highly bandwidth-hungry devices as peripherals. So, for example, you can connect an external SSD or external GPU with an acceptable level of performance.

Ultrabooks tend to have powerful processors, but lack memory and GPU power. Now you can take your MacBook home and connect it to these powerful peripherals, saving you the hassle of owning two computers. It also means that you can increase the GPU power of your desktop computer without having to buy a brand new laptop. There are many other use cases that take advantage of the massive bandwidth available thanks to the Thunderbolt 3 standard.

What about Thunderbolt 4?


At the time of writing, Thunderbolt 4 was announced by Intel at the 2020 Consumer Electronics Show. It is slated to debut in 2020 as part of Tiger Lake chips from the semiconductor giant, so by the time you read this it could very well be in consumer products.

However, there isn’t much to worry about here. Thunderbolt 4 is not a radical step up from Thunderbolt 3. Not in the way that Thunderbolt 3 completely pushed the previous generation out of the water.

The most important thing you should know about Thunderbolt 4 is that it is not faster in terms of bandwidth compared to Thunderbolt 3. So any performance concerns can be put to rest.

It is also not entirely clear what kinds of new features will be part of Thunderbolt 4, but the protocol will be tightly integrated with USB4, which will be as fast as Thunderbolt 3 and 4. All indications are that the two standards will be cross-compatible with each other and with Thunderbolt 3, which means users don’t really have to worry about what’s connected to what. This is now a future where we can all fall behind!

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