USB4, the next version of USB, is a reboot, a speedup, and a simplification of the ubiquitous connection protocol. Here's what you should know.
Simply call it USB4 on the floor: in 2021, a large wave of gadgets will use a new USB standard that goes beyond the normal performance enhancements. USB4, the latest version of USB, eliminates the gap (it's not "USB 4"—more on that later) and covers up some of the ambiguity that surrounds USB 3. Aside from the increased speeds, it also improves device compatibility and charging via the connection.
What is the origin of USB4? Partly based on older USB specifications; partly based on another interface. USB4 uses the Thunderbolt 3 protocol to give up to double the speed of the USB version it replaces. In addition to having higher capacity, USB4 can shuttle and prioritize file and video traffic more efficiently than earlier USB generations. And, on its physical ports, USB4 supports all of the old PC-connectivity crowd: Thunderbolt 3, USB 3.2, and USB 2.0 devices.
USB4 is expected to become widely available in 2021, although astute PC observers know it's already available in small quantities. The first computers with USB4 connectivity appeared at the end of 2020, and many more laptops and desktops with them are expected in 2021, along with USB4-compatible accessories.
Although USB4 should help clear up some of the confusion caused by the many varieties of USB 3 and they're various, shifting monikers ("USB 3.2 Gen 2x2"...seriously, folks? ), the new standard isn't a one-size-fits-all narrative. Here's all you need to know about USB4 taking over as the top dog in the Universal Serial Bus kennel from USB 3.2.
Pickup Speed: A New High of 40Gbps
One thing to keep in mind right away: the USB Implementers Forum (USB-IF) refers to USB4 as "USB4", with no space between the "USB" and the "4". We tell you this to help you with your online searches for the phrase. If searching for the word "USB 4" does not yield satisfactory results, eliminating the space may help.
USB4 incorporates the Thunderbolt 3 protocol, currently matching its highest transfer speed of 40Gbps. That is double the max speed (20Gbps) of the previous-generation USB, the ambiguously termed USB 3.2 Gen 2x2. Only a few ultrafast external SSDs (such as the Seagate FireCuda Gaming SSD and the SanDisk Extreme Pro Portable SSD v2) support that version of USB and suitable USB 3.2 Gen 2x2 connections are hard to come across.
Here's a nice cheat sheet to all of the USB versions that remain relevant today in PCs old and new, as a refresher on where USB has been, how the names have evolved, and where it is headed...
A Guide to USB Flavors in 2021
Because every USB deployment appears to be contractually bound to generate some level of consternation, here's USB4s: Not every USB4 device will be capable of 40Gbps transfers. Some USB4 items will only support a maximum speed of 20Gbps. Lower-cost items are likely to use just the slower speed, but you should verify the specifications of a specific USB4 device to determine what USB4 features it provides. Hardware manufacturers will be able to use a number of emblems to demonstrate USB4 capabilities...
To detect the difference in speed with USB4, search for the "20" or "40" in the logo on the box or spec sheet of the device you're considering.
It is worth noting that even the lower-speed (20Gbps) version of USB4 will provide greater transfer rates than most USB 3.2 implementations. Although USB 3.2 (the most current umbrella family of USB specifications in computers and peripherals) has a maximum bandwidth of 20Gbps in its USB 3.2 Gen 2x2 variation, USB 3.2 also comes in lower-speed variants. And they are far more prevalent, with peak speeds of only 5Gbps (USB 3.2 Gen 1) or 10Gbps (USB 3.2 Gen 2). (USB 3.2 Gen 2).
Concerning the USB-Thunderbolt Fusion
Thunderbolt has long been a proprietary Intel protocol that requires its own, specialized chip as well as a royalty charge paid to Intel, resulting in Thunderbolt never achieving the widespread acceptance that USB has. It appears exclusively on high-end PCs. In its most recent Thunderbolt move, Intel has reversed direction and made Thunderbolt available to other chipmakers without taking a portion. (For additional information, see our Thunderbolt 4 introduction and our Thunderbolt 3 vs. USB-C explanation.)
Because USB4 and Thunderbolt 3 have the same physical connector—USB Type-C (also known as USB-C)—this marriage is a natural match. The oval USB-C connection provides two benefits over "traditional" USB Type-A connectors (the older-style rectangular ones). For one thing, USB-C ports are smaller, allowing them to be integrated into thinner laptops and more compact gadgets. Another disadvantage of a USB-C port is that there is no up or down arrow. You can insert a USB-C cable into a USB-C port either way, which eliminates the hassle of trying to figure out which way is proper when connecting a USB device to your computer.
This collaboration of USB4 and Thunderbolt 3 also implies that future laptops with USB4 ports may be compatible with your old Thunderbolt 3 devices, which is potentially excellent news for gamers who use an external GPU. But why do we stress "could" and just mention "possibly" positive news? Because, according to the specification, adding Thunderbolt 3 compatibility into a USB4 port implementation is optional.
Thunderbolt 3 capability should be common among USB4 PCs now that manufacturers are no longer required to pay a tithe to Intel to add it. If, on the other hand, you're looking for a new laptop to go with your Thunderbolt 3 eGPU, it's a good idea to double-check the specs before making any assumptions.
Handling Video Signals with Brains and Brawn
In addition to collaborating with Intel to introduce the Thunderbolt 3 protocol to USB4, the USB-IF collaborated with the Video Electronics Standards Association (VESA) to improve USB4 display capabilities. The key element of the USB4 specification is compatibility for DisplayPort Alt Mode 2.0, which provides a massive amount of overhead for powering extremely high-resolution monitors.
A USB4 port can transmit up to 80Gbps of signal data with DisplayPort Alt Mode 2.0, allowing you to power multiple DisplayPort 2.0 displays with an 8K resolution at a 60Hz refresh rate or, in the distant future, a single 16K display at 60Hz. (Or more 4K screens than you probably have.) Because the display data being transferred is unidirectional, this is conceivable.
However, USB4 provides more than simply virtually limitless video capacity. USB4 can assign resources via the interface, allowing you to operate an HD display at up to 40Gbps while also handling a data transfer from an external SSD. Previous USB versions could only transfer video down one of its two lanes and data down the other, resulting in a 50/50 split at best. There is a dynamic allocation of resources with USB4. The lanes can be shared between video and data, providing the display the bandwidth it requires while enabling the remainder to be used for data transport. Consider what a USB4 hub could provide: the capacity to power all of the 4K screens you can fit on your desk while still leaving enough of bandwidth for high-speed data transfers.
Power Delivery for Everyone
USB Power Delivery is one feature you won't have to look up or seek on USB4 devices (USB PD). USB PD allows you to charge USB devices from your computer rather than from a power socket. All USB4 connections will support USB PD charging for your devices.
That is a departure from the current situation. Right present, some USB 3.2 ports support Power Delivery while others do not. You may charge your phone on any USB4 port on a laptop with USB4, and you won't have to look for a special USB PD-capable port or ports with the little lightning-bolt emblem. (That is if the PC manufacturer chose to include the logos in the first place.) Guessing the power capabilities of an unmarked USB port is perhaps the second-worst USB irritation, after constantly guessing incorrectly which way is up while attempting to put something into a USB Type-A port.
USB PD can supply up to 100 watts of power, which is more than enough to charge (inbound) most computers as well as charge (outbound) smaller devices such as an iPhone. Furthermore, USB PD offers just as much power as the device being charged can manage, so you don't have to worry about overcharging and damaging your phone's battery.
The USB4's Release
A few USB4-capable computers have already been released, as previously stated. Among other things, Intel's 11th Generation "Tiger Lake" Core CPUs will include native USB4 connectivity. PC Labs has tested a few Tiger Lake laptops, beginning with the Asus ZenBook 13 (UX325EA) and the Dell XPS 13 (9310) in late 2020. In 2021, every major laptop brand will receive a Tiger Lake upgrade.
Apple's new M1 MacBook Air, MacBook Pro, and Mac mini, which contain USB4 connectors, were introduced at the end of 2020. This year, anticipate some of Apple's other Macs to get an M1 facelift with USB4 capability.
Remember that, while backward compatibility means that your current USB 3. x peripherals will operate with a new, USB4-equipped laptop, these older devices will not be able to transport data at 40Gbps. They will be able to interact with your new laptop, but their maximum throughput will be limited by the older USB protocol they support.
We have yet to see a USB4 SSD or other devices in the wild, but existing portable drives with Thunderbolt 3 capability may deliver theoretical transfer rates of up to 40Gbps with a USB4-equipped PC. Remember the huge restriction from earlier: this type of peak speed is only possible if the PC supports USB4 at 40Gbps (rather than simply 20Gbps) and has particular backward compatibility with Thunderbolt 3.
By the end of the year, USB4 devices should outnumber Thunderbolt devices, and matching a new laptop with a new SSD for the quickest possible data transfers will be significantly easier, especially if those external SSDs have fast PCI Express cores. This, together with the ability to power one or more high-definition DisplayPort 2.0 displays from the same interface, heralds a new era of rapid connectivity-at least for those willing to spend on new systems and gear that can "4" it.
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