USB4 vs USB3 – What’s New with USB’s Latest Upgrade?

What is USB4?

As defined by the USB-Implementers Forum, the USB4 specification is the next generation of USB performance. With constant advances in technology becoming expected by everyday consumers, higher data performance is necessary to facilitate the digital experience they need. 

Expanding on its predecessors’ (USB 3.2 and 2.0) progressive architectures, the USB4 specification was designed to offer the highest USB bandwidth available to extend USB-C performance. USB4 offers a connection that provides the best possible bandwidth while still maintaining compatibility with existing USB 3.2, USB 2.0, and Thunderbolt™ 3 hosts and devices. 

Built on the Thunderbolt™ 3 protocol specification contributed by Intel, USB4 doubles the existing maximum aggregate bandwidth of previous USB iterations and enables multiple simultaneous data and display protocols.

USB-IF elaborates: 

USB4 defines a method to dynamically share a single high-speed link with multiple end device types to best serve the transfer of data by type and application. As the USB Type-C connector has evolved into the role as the external display port of many host products, the USB4 specification provides the host the ability to optimally scale allocations for display data flow.

Key characteristics of the USB4 solution include:

  • Two-lane operation using existing USB Type-C cables and up to 40 Gbps operation over 40 Gbps certified cables*
  • Multiple data and display protocols to efficiently share the maximum aggregate bandwidth over the bus
  • Backward compatibility with USB 3.2, USB 2.0 and Thunderbolt™ 3

*Additionally, USB4 devices are required to support a minimum speed at 20Gbps. A full 40Gbps transfer rate requires the use of USB4 Gen 3 certified cables. 

The Core Specs of USB4

Though some USB Type-C devices support USB Power Delivery (USB PD), it is not required for this specific standard. However, all USB4 devices and hosts are required to comply with this USB PD. Due to this standard, higher wattages and better power management are available.

In theory, USB PD can provide up to 100 watts, however charging devices do not have to support that wattage. Essentially this means that a USB4 port will provide power, however it may not be the same wattage as the host machine.

While you can use USB-C for “fast charging,” it’s possible to plug in a device and receive a “charging slowly” notification. USB4, however, has to comply with the USB PD specs, so every USB4 cord will request higher currents and voltages from chargers. You can also charge more devices from a single port.

Cable Length  
Recommended cable lengths are par for the course when it comes to USB and a USB4 cable is no different. Official USB4 cables are currently maximized at .8 meters (~2.6 ft). Longer cables are available on the market, but don’t meet the USB4 standard. The best way to get a longer USB4 cord is to connect several together with an active USB adapter, which adds a power port to the next step, boosting data. These are generally powered with a separate power adapter, or they may take up a port on your computer. 

USB4 supports older USB devices, as long as they fit into the port. If they don’t, consider buying a converter. You’ll just need to know if your older USB tech uses a USB-A or USB-C design.

Data Throughput   
USB4 has data transfer speeds of up to 40 Gbps, almost twice the speed of USB 3.0, allowing you to transfer high-capacity files in seconds. Where things like heavy design-laden graphics files, 4K movies, effects and graphics used to take long stretches of time to transfer, now they’ll be quite a bit faster. This technology also ensures that connection to multiple monitors and external displays is supported at high resolutions.

USB4 Specs

Mode NameOld NameDual-LaneSpeed (Gbps)Maximum LengthUSB-IF Name
USB 3.2 Gen 1x1USB 3.0
USB 3.1 Gen 1
No52mSuperSpeed USB 5Gbps
USB 3.2 1x2Yes102m
USB 3.2 Gen 2x1USB 3.1 Gen 2No102mSuperSpeed USB 10Gbps
USB 3.2 Gen 2x2
Yes201mSuperSpeed USB 20Gbps
USB4 Gen 2x1No101m
USB4 Gen 2x2Yes201mUSB4 20Gbps
USB4 Gen 3x1No20.8m
USB4 Gen 3x2Yes40.8mUSB4 40Gbps

USB4 & Thunderbolt™ 4

For simplicity's sake, it’s fair to say that Thunderbolt™ 4 is just USB4 with a stamp of approval from Intel indicating that the manufacturer’s cable is up to snuff. Essentially, it will still offer 40Gbps connectivity and be backwards compatible with Thunderbolt™ 3 devices. Some USB4 high-end features are “optional” to manufacturers and the Thunderbolt™4 label is simply recognition that all the features are represented. 

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