Everything you need to know about USB4

Prepare for a whole new USB generation. “USB4” (the official spelling lacks a space, but we’re using one in this article to reflect how readers search) is finally showing up in some shipping computers, including Apple’s new M1-powered iMacs, Macbooks and Mac Mini, and laptops with Intel 11th Gen Tiger Lake laptops. While there aren’t many USB 4 devices on the market right now, a new generation of USB 4-powered docks and peripherals is on the way.

Faster transfer speeds, better video bandwidth management, and possible Thunderbolt 3 compatibility are just a few of the advantages USB 4 promises.

The thought of a new standard could sound daunting in a market where PC and peripheral makers utilize a dizzying variety of USB version numbers to sell their products. There is, however, a lot to look forward to. Everything you need to know about USB 4 is right here.

The Most Important Advantages of USB 4

The new USB 4 standard has three major advantages over previous USB versions.

  • 40 Gbps Maximum Speed: Devices can function at up to 40 Gbps utilizing two-lane cables, which is the same speed as Thunderbolt 3. The data is sent in two sets of four bidirectional lanes in each direction.
  • DisplayPort Alt Mode 2.0: USB 4’s alternative mode supports DisplayPort 2.0. DisplayPort 2.0 supports 8K resolution at 60 frames per second and HDR10 color. Because it transfers all data in one direction (to the display), DisplayPort 2.0 may use all eight data lanes at once, it can use up to 80 Gbps, which is double the amount available for USB data.
  • Thunderbolt 3 devices are supported: Some USB 4 implementations, but not all, will also function with Thunderbolt 3 devices.
  • Better Video and PCIe Resource Allocation: Instead of using alternative mode, which switches the connection to the other interface, USB 4 devices can employ “protocol tunneling,” which sends DisplayPort, PCIe, and USB packets at the same time while allocating bandwidth appropriately.
  • So, if the video only requires 20% of the bandwidth to drive your 1080p monitor, which also serves as a hub, the other 80% may be used to transport information from your external SSD, which can be connected through USB or PCIe.

Type-C Ports Will Be Used

It should go without saying that USB 4 will only work with the Type-C connector. It’s unlikely that a USB 4 device or hub will include Type-A ports. Other contemporary standards, such as USB Power Delivery, only operate with Type-C, so this isn’t surprising. If you use an adaptor to connect to a Type-A 5 Gbps USB 3 connection, for example, the speed and power will be reduced to the lowest common denominator.

Optionally compatible with Thunderbolt 3

Intel made headlines when it announced that it has donated the Thunderbolt 3 protocol to the USB Promoter Group, allowing Thunderbolt 3 devices to connect to USB 4 devices and Thunderbolt 3 devices to connect to USB 4 devices. That’s great news for everyone, especially laptop gamers who wish to use an eGPU to play games (external graphics card).

Despite the fact that there are a lot of Thunderbolt 3 eGPUs available, few laptops and desktops have Thunderbolt 3, and nearly no motherboards support Thunderbolt 3 out of the box. You won’t find Thunderbolt on any AMD-powered PC because it’s an Intel standard. Because Thunderbolt 3 is not an open standard and requires an extra chip, it is also more expensive to install than conventional USB. So, whether you want an eGPU or a super-fast Thunderbolt 3 storage drive, your options are restricted today.

With USB 4, device and host manufacturers will not be required to pay Intel any royalties, ensuring widespread adoption. But there’s a catch: Thunderbolt compatibility isn’t required by the USB 4 specification, so manufacturers aren’t obligated to adopt it. You might buy a laptop with USB 4 only to discover that it doesn’t function with your Razer Core X graphics dock, for example.

“We expect PC OEMs to broadly embrace Thunderbolt backward compatibility,” said USB Implementers Forum Chairman Brad Saunders. “Most of what they require is already included into the USB 4 design.” “Because it’s built on the same technology, we expect a high rate of adoption there,” he says. “However, the phone companies are likely to opt out of adding the additional tiny bit they need to be backward compatible.”

So far, Apple’s M1 machines include Thunderbolt 3 / USB 4 connectors, while new Tiger Lake laptops like the Dell XPS 13 claim to have USB 4 / Thunderbolt 4. Despite having these connectors, the latest Macs aren’t compatible with external GPUs.

It’s crucial to remember, too, that Thunderbolt 3 and Thunderbolt 4 are Intel logo certification processes that cost manufacturers time and money to implement. So, while a USB 4-powered computer could function with 40 Gbps devices or even those labeled as Thunderbolt, if it doesn’t go through certification, it won’t be identified as supporting Thunderbolt.

It’s also understandable that a phone or tablet manufacturer would save money by not offering 40 Gbps transfer speeds or PCIe data transmission capability. You wouldn’t (and couldn’t) link your phone to a high-performance external SSD or an eGPU.

USB 4 has two speeds.

Despite the fact that it can theoretically reach rates of up to 40 Gbps, not all USB devices or hosts will support it. Expect Smaller and less expensive devices, such as phones and Chromebooks, will be able to use the USB 4 20 Gbps version, which is still far quicker than the USB 3.x 5 Gbps connection used in most laptops today (though 10 and 20 Gbps USB 3.2 connections do exist). If you want the quickest USB 4 connection available, make sure you read the specifications.

Version Numbers Will Not Be Used on USB 4 Labels

So, how can you know if the device you’re buying supports USB 4? The USB-logo IF’s program focuses solely on the connection’s transfer speed, which is either 20 or 40 Gbps. Manufacturers may include USB 4 in their spec sheets, but the USB-logo IF’s program focuses solely on the connection’s transfer speed, which is either 20 or 40 Gbps.

The certification marks will be identified as USB 20 Gbps or USB 40 Gbps, or the USB trident logo with a 20 or 40 next to it, which you’ll see on retail packaging and occasionally on the devices themselves.

It’s worth noting that there’s also a SuperSpeed USB 20 Gbps standard, which is technically USB 3.2, but lacks the additional characteristics of USB 4. That, on the other hand, would have a distinct logo.

It’s also worth noting that many of the millions of USB products on the market lack official USB-IF certification, preventing them from using these logos. Consequently, despite the organization’s best efforts, many products will undoubtedly use the name USB 4 in their product descriptions.

When it comes to sharing bandwidth between video and data, this device excels.

Protocol tunneling, the ability to dynamically modify the amount of resources available when transferring both video and data over the same link, is a key aspect of the USB 4 spec. Let’s imagine you have a USB 4 port with a maximum speed of 40 Gbps and you’re using it to output to a 4K monitor while copying a large number of files from an external SSD. Let’s say the video feed requires approximately 12.5 Gbps. In such instance, USB 4 will give your backup disk the remaining 27.5 Mbps.

The ability to transmit DisplayPort / HDMI video from a Type-C connection was added with USB-C, but the current 3.x spec doesn’t give a good mechanism to split up resources. DisplayPort alt mode, according to Saunders, may share bandwidth 50/50 between USB data and video data, whereas HDMI alt mode does not enable simultaneous USB transmission at all.

Protocol tunneling, on the other hand, sends DisplayPort, PCIe, or USB as data packets, allowing USB 4 to regulate resource allocation.

“We didn’t have quite the flexibility in architecture with USB SuperSpeed to truly manage those two unique bandwidths [data and video] in a combined approach through the port,” Saunders explained. “As a result, this is truly tuned for higher scalability across the various application kinds.”

USB PD is supported by all USB 4 hosts.

While some USB Type-C devices today implement the USB Power Delivery (USB PD) specification for delivering power to high-powered devices, not all of them do. USB PD will be required of every USB 4 device and host, allowing for greater wattages and improved power management.

Although USB PD can theoretically deliver up to 100 watts, charging devices do not have to be able to handle that much power. So there’s no guarantee that a certain USB 4 port will provide the amount of power that a specific notebook demands, but you can expect it to comply with the specification.

Older Devices Are Backward Compatible

The best feature of all USB generations is how nicely they all function together. USB 4 devices and ports are compatible with USB 3 and USB 2 ports. It should go without saying that you’ll only get the speed and capabilities of your connection’s weakest link. When you attach a USB 4 device to a USB 3.2 port, it won’t be able to transfer at 40 Gbps, and an old-school USB 2 port won’t suddenly become quicker just because you connect it to a brand new USB 4 backup drive.

Your old cables will operate at full speed.

Your existing USB cables and adapters will work with USB 4, but they will only operate at their maximum rated speeds, like with anything else that is backward compatible. So, even if you use a USB 3.2 cable that can transfer data at 5 Gbps to connect a USB 4 port to a USB 4 device, you’ll only get 5 Gbps. You’ll almost certainly need a Thunderbolt 3 cable to get Thunderbolt 3 support.

Thunderbolt 4 is essentially USB 4 with all of the trimmings removed.

At the same time as USB 4 is gaining traction, Intel’s Thunderbolt 4 is making its debut, yet the two standards aren’t truly competing. To be certified as Thunderbolt 4, a computer or peripheral must first obtain an Intel certification demonstrating that it is capable of supporting all of USB 4’s features, including Thunderbolt 3 support.

Thunderbolt 4 is merely a marking that certifies that this device has been approved by Intel at a cost to the manufacturer. When a product advertises Thunderbolt 4 functionality, what it truly implies is that it’s a USB 4 device with 40 Gbps connectivity and Thunderbolt 3 backward compatibility. However, as we’ve seen, even computers that are “Thunderbolt 3” compliant, such as the new Apple MacBook Pro, may not work with Thunderbolt 3 eGPUs.

Thunderbolt 4 is a branding program, according to Saunders. “And, as Intel has stated, the branding program is effectively USB 4 with some restrictions that it support all of the high-end functions, some of which are optional.”

Manufacturing Will Be More Expensive Than USB 3.2

The increased cost of USB 4 is one barrier to widespread adoption. While we don’t know how much adding USB 4 connectivity to PCs and devices would cost, we do know that it will necessitate more expensive components than the present standard, USB 3.2.

“I believe it will be less than Thunderbolt, but not as cheap as SuperSpeed in terms of material costs to the device developer,” Saunders predicted. “It takes a lot of gates to achieve it, but the product still does all of the SuperSpeed stuff,” says the developer.

Saunders went on to say that he hopes the costs would drop fast. However, we believe that, at least initially, the pricing difference will force USB 4 onto higher-end PCs.

Why is USB 4 Officially Spelt “USB4”? (No Space)

The new spec is officially spelled without a space before the version number, unlike every other version of USB. Although we believe most people will refer to it as USB 4, the official name is USB4. The purpose of removing the gap, according to USB Promoter Group CEO Brad Saunders, was to shift the focus away from version numbers and onto a brand name.

He told us, “One of the things I’m trying to convey right now is that we don’t plan to go down the 4.0, 4.1, 4.2 iterative road.” “We also don’t want it to be associated and utilized as a distinction with items… we want to keep it as basic as possible.”

The USB 3.x specification contains a plethora of version numbers, including USB 3.0, USB 3.1 Gen 1, USB 3.1 Gen 2, and four different versions of USB 3.2, as well as the existence or absence of optional features like USB PD and alternative mode. But, according to Saunders, those figures are mostly for developers, and he wants OEMs would sell their devices using simpler terminology like “SuperSpeed USB.”

Saunders stated the group will not utilize version numbers for spec revisions, maybe because he is concerned about marketers bombarding customers with too many digits. So, even if a faster version comes out in two years, it’ll probably still be named USB 4, but with a speed number following it (we imagine something like USB 4 80 Gbps). Because he and his team have yet to decide on a branding approach, USB 4 may have a marketing name. USB 4 may be given its own moniker, similar to how USB 3.x is known as “SuperSpeed USB.” (We suggest “Super Duper Speed USB”).

“I’d like for there to be a clear separation.” “Try not to be hooked on these dot releases for every single speed,” he warned, adding that USB 4 has its own design with its own set of speeds. “We’ll simply have the speedier version of the certification and the brand if and when it goes faster.”

Today’s USB 4 Products

There are only a few products that are marketed as “USB 4” devices as of this writing. The Kingston SD5700T docking station, an Acasis M.2 NVMe container, an OWC Thunderbolt Hub, and a Cable Matters 40 Gbps cable are among the items on the list.

You can use USB 4 to connect to Thunderbolt 3 docks, eGPUs, and high-speed SSDs even if you don’t have any specific USB 4 devices.


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