A new version of the USB protocol is set to be revealed in November by the USB Implementers Forum (USB-IF), adding to an already complicated landscape of ports, cords, and devices.
The size and shape of USB ports are not changing. The new standard will be fully compatible with cords and devices using the old standard. USB4 will enable more capabilities and faster transfer speeds.
Before we get into the new USB4 version 2.0 and the recently released (but yet to be widely adopted) USB4 standards, a little explainer and history lesson about USB technology.
USB History Lesson
USB, which stands for Universal Serial Bus, was released in 1996 and was intended to simplify and unify how computers and devices interact together. Prior to its invention, computers relied on a variety of ports to communicate with devices. A printer may have been plugged into a serial port, a monitor was plugged into a VGA or CGA port and a game controller was plugged into either the serial port or a dedicated “game port,” while keyboards and mice were typically plugged into a PS/2 port, though some early keyboards were also plugged into a serial port.
This all changed with the advent of USB, which simplified the process and allowed all of the above, excluding monitors, to be plugged into one type of port. This made things simple for both the consumer, who no longer had to remember what kind of ports their device had, and the manufacturers, who were able to work with one standard while appealing to the majority of computer users.
A quick note for the layman: bits versus bytes goes back to the early days of computers and how data was stored and transferred. When you have a storage device, like a hard drive, it is usually measured in bytes rather than bits. The same is true when transferring or downloading data: your computer will typically display the progress in bytes (kilobytes, megabytes, gigabytes) rather than bits (kilobits, megabits, gigabits). Because of how computers transfer data, standards for technologies (along with your ISP’s claimed speeds) are usually expressed in bits. Eight bits equal one byte. In abbreviations, the difference is expressed in capitalization: MBps for megabytes per second, and Mbps for megabits per second.
The first implementation of USB (1.0) was extremely slow by today’s standards. It was capable of transferring data at a rate of 1.5 Megabits per second (Mbps) or 187.5 Kilobytes per second (KBps). USB1.1 upped that greatly, to 12 Mbps.
In the year 2000, USB2.0 increased the data transfer rate to 480Mbps, and then in 2008, USB3.0 increased that to 5Gbps. Most recently, USB3 Gen 2x2 upped that to 20Gbps.
During all that time, the ports for USB stayed roughly the same shape, and a USB3.0 cable will theoretically work with a USB1.0 port or vice versa, though speed will always be limited to the lowest standard being used (so a USB3.0 port will perform at USB1.0 speeds if a USB1.0 cable is used).
Does Size Matter?
Different devices have required smaller ports, resulting in another tree of evolution for the USB standard. The typical USB port, the kind you find on most computers and seems to always be flipped to the wrong side when you attempt to plug it in, is called USB-A. USB-B is a square connector that is rarely seen these days and is typically used for older printers and similar devices. USB-C is the smaller, newer shape typically seen in Android phones and many newer laptops today. Unlike USB-A and USB-B, USB-C is reversible. All of them are compatible with each other, so it is not atypical to see a cord with a USB-A port on one end and a USB-C port on the other.
There are also mini-USB and micro-USB, which were typically used on older and cheaper Android devices, though those are quickly being replaced with USB-C ports. By the fall of 2024, the European Union will require USB-C ports on all smartphones, tablets, digital cameras, and similar devices.
Further complicating the matter is Intel’s proprietary Thunderbolt USB standard. Intel broke from the USB-IF and created its own backward compatible standard that offers faster speeds and more features than the USB-IF standard. To use the latest version of Thunderbolt, companies have to pay Intel royalties. Intel’s newest standard is Thunderbolt 4. The first Thunderbolt standard was compatible with both PCIe and Displayport, allowing even more devices, including monitors, to be plugged into USB ports.
USB4 Version 2
With all that in mind, we can finally discuss USB4 and USB4 Version 2 and what it means for future devices. Intel dropped the royalties on Thunderbolt 3 in 2019. The USB-IF built on Thunderbolt 3 and USB3 Gen 2x2 to create USB4.
To be called USB4, ports and cables have to be capable of transferring data at 20Gbps, though many will be able to go to 40Gbps. When USB4 version 2 is released, it will be able to transfer data at 80Gbps. That will exceed Thunderbolt 4’s max data rate transfer of 40Gbps, but Intel may soon release Thunderbolt 5.
While USB3 could be used for monitors, the performance was often lacking and limited in resolution. USB4 will be capable of running four 1080p monitors running with a 120hz refresh rate (the speed a monitor updates images) at once, two 4k monitors running at 120hz, or one 8k monitor running at 30hz.
USB4 also supports protocol tunneling. This allows devices to use only the amount of data they need, so a monitor may use 10Gbps while a hard drive uses the remaining 30Gbps. Previous iterations could split bandwidth, but it could not prioritize based on each device’s need, so with a USB Gen 2x2 port and cable, a monitor and hard drive would have to split the available bandwidth, 20Gbps, evenly.
PCIe support will also be available, but not required, for USB4 devices. PCIe ports are used to enable the most direct and fastest connection to a computer. Typically embedded into the computer’s motherboard, they are most commonly used for GPUs (video cards), which are computer components that process video, computer graphics, and other advanced tasks not handled by the CPU. PCIe in recent times has also been used for storage and network devices.
Using PCIe lanes through Thunderbolt or USB4 enables components, like GPUs, to be plugged into a USB port. This has enabled enthusiasts to plug desktop video cards into laptops with Thunderbolt, greatly increasing their performance (but also bulk). In the future, this could be used to create GPU docks, allowing portable devices to use much more power when plugged into a dock at home, while still maintaining portability when unplugged. However, no such devices currently exist using either Thunderbolt or USB.
What it All Means
Essentially, USB4 catches the standard up to Thunderbolt 4 in almost every way, with a few exceptions. As mentioned, PCIe is supported but not required in USB4 but is required in Thunderbolt 4. However, both will transfer at a rate of 32Gbps when using PCIe. USB4’s minimum transfer speed is 20Gbps and its maximum is 40Gbps, while Thunderbolt 4’s minimum and maximum speed is 40Gbps. USB4 ports also must have a minimum power output of 7.5W, up from 4.5W with USB3. Thunderbolt has a minimum power output of 15 W. Meanwhile, USB4 cables need to be capable of transferring either 60W or 240w of power. Thunderbolt 4 cables can transfer 100W of power.
Thunderbolt also requires that laptops can be charged over the Thunderbolt USB port and that the PC can be woken up when a device is plugged into the port, while USB4 does not have those requirements.
The most significant change, however, is that USB4 will not require licensing fees, unlike Thunderbolt 4. This will allow devices made by Intel’s competitors, like AMD, along with smaller companies who cannot afford the licensing fees, to access many of the features and speeds previously only possible with Thunderbolt 4.
The USB-IF will be issuing badges for devices to differentiate between USB4 devices capable of 40Gbps and 20Gbps along with USB3 Gen 2x2 devices, but those badges will require certification from the USB-IF and many companies are likely to forgo that cost. For that reason, it is suggested that consumers look at the device’s spec sheet to ensure they are getting the version of USB4 that best suits their needs.
In short, USB4 devices and cables will be capable of transferring data quicker, provide more power to connected devices, support more and faster monitors, and allow more devices, like GPUs, to be plugged into USB ports when compared to older iterations of USB.
The full specifications of USB4 Version 2 are expected to be released in November.