What Is Thunderbolt 4 All About? Why Does This New PC Interface Matter?

Thunderbolt 3 has definitely been on the minds of anyone who has used a Mac laptop in recent years, or a high-end Windows notebook, and has left them scratching their heads as to what it can achieve. This port resembles the new-style oval USB Type-C connectors, although it has a lot more capabilities: It can transport a video signal using the DisplayPort protocol, charge connected devices, and transfer data at speeds that are faster than USB. (For more information, see our article Thunderbolt 3 vs. USB-C: What’s the Difference?)

However, the narrative of the latest Thunderbolt interface, Thunderbolt 4, begins with a shift in focus. The Thunderbolt 3 protocol was made available to USB’s controlling consortium (the USB-IF) for royalty-free usage in the development of USB4 devices, allowing for greater speeds and interoperability. The fortunes and paths of the two new “4” specifications are inextricably linked. (Yes, the USB team removed the space from “USB4”.) That isn’t a mistake.)

However, Intel did not abandon development of its typically proprietary Thunderbolt specification as a result of this move toward open source. Intel has continued to advance Thunderbolt, announcing Thunderbolt 4 at CES 2020 a year ago, and new Thunderbolt 4-equipped PCs based on Intel’s 11th Generation (“Tiger Lake”) Core CPUs are only now beginning to hit the market. Because Thunderbolt 4 and USB4 are both arriving at the same time…and often on the same physical ports on these Tiger Lake-based systems, there is certain to be some confusion.

Thunderbolt 4’s lack of a single headline-grabbing feature, like as a quicker top-end speed than its predecessor, also muddles the picture. Thunderbolt 4 isn’t a race; it’s more about meeting minimum requirements than going fast. To help you understand how Thunderbolt 4 differs from Thunderbolt 3 and USB4, we’ve put together a quick primer on the current state of affairs.

A Brief History of Thunderbolt

Before we dive into the details of the new Thunderbolt 4 protocol, let’s go through what Thunderbolt is and what it does, as well as how we got here.

Thunderbolt was first seen on a MacBook Pro in 2011, thanks to Intel and Apple. The port was physically a tiny DisplayPort connector with a small lightning-strike icon next to it. It merged DisplayPort and PCI Express technologies in a single connection to support high-resolution screens and 10Gbps data transfers. Thunderbolt 2 increased the bandwidth to 20Gbps and introduced DisplayPort 1.2 capability, allowing the interface to drive a video stream to a 4K monitor using the same physical connector.

Thunderbolt 1 to 4: The Basics

VersionYear IntroducedPeak Rated ThroughputConnector Type
Thunderbolt 1201110Gbpsmini DisplayPort
Thunderbolt 2201320Gbpsmini DisplayPort
Thunderbolt 3201540GbpsUSB Type-C
Thunderbolt 4202040GbpsUSB Type-C

Thunderbolt 3 quadrupled the data bandwidth to 40Gbps once more. Another significant change is that Thunderbolt 3 no longer uses the tiny DisplayPort connector as its physical interface, instead opting for the USB Type-C port, with the technology relying on it in the same way that Thunderbolt 1 and 2 did. It also offered up to 100 watts of electricity via USB Power Delivery (USB PD), allowing you to charge your phone and other USB devices from your PC—or even charge a laptop. Thunderbolt networking with 10Gbps Ethernet was also featured in the Thunderbolt 3 specification. Thunderbolt 3’s video bandwidth was sufficient for a variety of uses, ranging from single-cable docks that could also charge your devices to external GPUs that might boost a laptop’s graphics performance.

What’s the Difference Between Thunderbolt 4 and Thunderbolt 3?

Thunderbolt 4 does not provide any notable enhancements over Thunderbolt 3. The two methods appear to be extremely similar on the surface. Both use the physical USB Type-C connector. Both have a 40Gbps maximum throughput. Both provide charging power of at least 15 watts and up to 100 watts. Furthermore, both support 10Gbps networking.

Thunderbolt 4 features a lot of major improvements underneath the surface. For starters, it doubles Thunderbolt 3’s minimum video and data needs. Thunderbolt 4 will allow video signals to be sent to two 4K monitors or one 8K display, whereas Thunderbolt 3 can only handle a single 4K display. Thunderbolt 3 systems must handle a maximum data throughput of 16Gbps via PCI Express, however Thunderbolt 4 will increase that to 32Gbps. Anyone who often uploads massive quantities of high-resolution video and other large data sets from storage drives to their PC for editing would appreciate the extra bandwidth.

USB4 vs Thunderbolt 4 wires
Intel

Thunderbolt 4 will also make peripherals more competent. Thunderbolt 4 docks and monitors will include four Thunderbolt 4 ports, which is double the two ports found on Thunderbolt 3 products. New thin-and-light laptops with charging requirements of less than 100 watts must include USB Type-C charging on at least one Thunderbolt 4 connector. A Thunderbolt 4 laptop must also be able to wake up from sleep when connected to a Thunderbolt 4 dock through a linked keyboard or mouse. Thunderbolt 4 cables will also offer 40Gbps throughput at up to two meters in length, compared to a passive Thunderbolt 3 cable’s maximum of 0.5 meters.

You may daisy-chain up to six Thunderbolt devices, allowing you to connect many devices without requiring each one to have a direct connection to your computer. You’ll have more choice in setting up your workspace with Thunderbolt 4’s greater charging and wake-from-sleep capabilities, as well as longer cords, to make your office less crowded with wires and your office life a little easier.

The Differences Between Thunderbolt 4 and USB 4

In practice, Thunderbolt 4 and USB4 are frequently confused. The USB Type-C connector is used by both devices. They both have a 40Gbps maximum bandwidth. Intel’s new 11th Generation “Tiger Lake” Core processors will be used in both of them. Thunderbolt 4 also supports USB4, allowing you to connect a USB device to the Thunderbolt port on your laptop. Thunderbolt 4 is also Thunderbolt 3 backward compatible. However, in both cases, the connection will default to the slower USB4 or Thunderbolt 3 speeds.

Thunderbolt 4 is essentially a guarantee that you’re getting the latest and greatest USB4 version. While USB4 has the same 40Gbps transfer rate as Thunderbolt 4, it also has a 20Gbps version. Thunderbolt 4 also ensures that you can run at least two 4K displays and transport data at speeds up to 32Gbps. Only the bare minimums of a single display and a 16Gbps data throughput are guaranteed with USB4. A USB4 hub also lacks Thunderbolt 4’s required charging and wake-from-sleep features, as well as 10Gbps networking.

Thunderbolt 4 vs USB4: The Basics

Minimum SpeedMaximum SpeedMinimum Video RequirementsMinimum Data Requirements
Thunderbolt 440Gbps40GbpsTwo 4K displays @ 60Hz32Gbps
USB420Gbps40GbpsOne display @ 60Hz16Gbps

Thunderbolt 4 does have one advantage over USB4: more informative logos. When using USB4, look for the “USB 20Gbps” and “USB 40Gbps” emblems next to USB Type-C ports to determine which USB4 flavor you’re using. Unfortunately, Intel’s Thunderbolt branding do not include such details. A Thunderbolt logo is a Thunderbolt logo, and there’s no way to identify whether a port is Thunderbolt version 1, 2, 3, or 4 by looking at the side of your laptop or desktop PC’s I/O panel. (The connector will tell you if it’s Thunderbolt 1 or 2 versus Thunderbolt 3 or 4, but you can only guess based on appearances.) To find out which Thunderbolt version a device supports, examine the user manual or spec sheet. (Some Thunderbolt 4 cables may have a “4” next to the Thunderbolt 4 emblem, however computers rarely offer such specificity.)

Anti-Thunderspy Protection

Last but not least, Thunderbolt 4 has improved security against Thunderspy attacks than Thunderbolt 3. A hacker could steal your data using the weaknesses of a Thunderbolt port in such an assault. Even if your laptop is locked or asleep, or your hard drive is encrypted, such an assault only takes five minutes and requires physical access to your device.

The PCI Express element of Thunderbolt and its direct memory access (DMA), which bypasses the CPU to permit quick access to system memory, are used in a Thunderspy attack. Intel’s Virtualization Technology for Directed I/O (VT-d), which guards against DMA assaults, is required for Thunderbolt 4.

Here’s how it works: DMA remapping is a feature of VT-d that isolates a piece of system memory for a connected device, preventing it from reading or writing to other parts of your memory. It basically blocks a Thunderbolt device’s access to other parts of the system memory, preventing it from overwriting things like your device’s password security.

To be sure, most people are unlikely to be affected by this vulnerability. It’s mostly a worry for corporate laptops that travel frequently, are left in unprotected settings, and hold highly sensitive financial or other business information.

Arrival of Thunderbolt 4: Rolling Thunder

Thunderbolt 4 laptops with Intel’s 11th Generation “Tiger Lake” Core CPUs are only now beginning to hit the market. Last fall, we saw the first Tiger Lake laptops with Thunderbolt 4 connectivity in the latest Asus ZenBook 13 (UX325EA) and Dell XPS 13 models (9310). There will undoubtedly be more, but not every Tiger Lake laptop with USB-C ports will enable Thunderbolt 4. Look for the Thunderbolt emblem on the spec sheets, because if you don’t see it, you’re looking at a regular USB4 port with previous-generation Thunderbolt 3 capabilities.

While Apple’s new M1 MacBook Air, MacBook Pro, and Mac mini were released near the end of 2020, they did not include formal Thunderbolt 4 capability (just Thunderbolt 3). It’s unclear when the first Mac with Thunderbolt 4 will be released, or whether it’ll be built on Apple’s own M1 silicon or Intel Tiger Lake processors.

OWC
 OWC

On the periphery, the first Thunderbolt 4 docks were starting to hit the market with announcements at CES 2021 (see this example from Kensington and this example from OWC), while hubs, external drives, external GPUs, and screens appeared to be on the horizon. They’ll almost certainly start appearing later this year as more Thunderbolt 4 PCs and laptops are produced.


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