USB ports, bandwidth of its different versions

Universal serial bus is a protocol for communicating devices to a computer through a port or interface that is used to communicate them. The USB port is what enables our digital cameras, printers, scanners, cell phones, hard drives, etc. Its development began in 1994 with the USB Implementers Forum and is technically an evolution of the SIO port on Atari computers. Out of curiosity, several of the engineers who worked on USB had worked on creating the SIO port in the late 1970s for the 8-bit Atari.

The origins and the first generation of USB

The first USB ports became available in late 1995, but very few peripherals used them. Version 1.0 of the standard had a bandwidth of 12 Megabits per second, which was much more than what some common peripherals like keyboard and mouse that worked at the time on PS / 2 type ports at 99%. computers needed.

This led to the creation of the USB 1.1 standard, which was no faster than 1.0, but had a low power mode that allows it to run at 1.5 Mbits per second. Even with the reduced bandwidth, this was a significant leap from conventional PC peripheral ports. Like the parallel port, which only transmitted 800 Kbits per second and the serial ports which ranged from 115 to 450 Kbits per second.

But what made USB popular was the large number of interfaces available and the incompatibilities they generated in the I / O controller of PCs. USB was therefore born with the aim of solving this problem. With companies like Intel, Microsoft, Compaq, LSI, Apple, and Hewlett-Packard among its main supporters, it was quickly included in most computers as a standard port.

Hi-Speed ​​USB, the biggest jump in bandwidth

Version 2.0 of the standard represented a qualitative leap from version 1.0 of the standard. Maintained backward compatibility with USB 1.1. The second version of the standard increased the bandwidth from 12 megabits per second to 480 megabits per second. Being the most spectacular jump ever in the history of the USB standard, since we are talking about a 40-fold jump in terms of bandwidth.

The increased bandwidth made it possible to accommodate two new types of devices which, due to the speed limitations of USB 1.1, suffered a bottleneck that affected their performance. The first of these was external hard drives, and the second was video cameras. It has not been in vain until then that it was common to use Gigabit Ethernet or IEEE-1394 interfaces, colloquially known as FireWire port, for this type of peripheral.

The speed of USB 2.0 makes it possible to relocate the FireWire port in PCs, which was not used except in the Apple Macintosh where it was standard. On a PC, on the other hand, it was not usual to see this port and gradually hard drives and cameras began to adopt the USB 2.0 port with FireWire, when even Macs started using the second version. from USB, the IEEE-1394 has disappeared.

Another novelty offered by the USB 2.0 standard was the ability to power peripherals from the USB port itself. Thanks to the fact that the port has changed from 100mA of USB first generation current to 500mA of USB 2.0

USB Super Speed ​​and the arrival of Type C

A decade after the launch of the USB port, version 3.0 of the standard or better known as USB SuperSpeed ​​was introduced. With an increase in its bandwidth which went from 480 Mbits per second to 4.8 Gbit / s and being fully backward compatible with version 2.0 of the standard. As for its capacity to supply peripherals, it is more important since it went from 500 mA to 900 mA.

The new standard brought about major changes in the lineage of different types of USB ports, which resulted in the creation of new USB interfaces. Arguably, USB 3.0 ports are designed so that you can connect a USB 2.0 cable, but not the other way around, since the 2.0 and 1.0 interfaces do not have the pins needed for USB 3.0 compatible devices. To make things easier for the novice user, the USB 3.0 ports use the color blue.

In 2013 and five years after the introduction of USB 3.0, its upgraded version was released as USB 3.1. Among its novelties, the fact of doubling the bandwidth and going from 900 mA to 1.5 amps when supplying peripherals. From USB 3.1, a new variant of USB has been created, USB type C. This has not extended the bandwidth, but its amperage, from 1.5 amps to 3 amps.

The third and last version of USB SuperSpeed ​​was 3.2, introduced in 2017 and again doubling the bandwidth to 20 Gigabits per second and with the ability to power devices with 5 amps. Thanks to the increase in the speed of USB 3.1 and USB 3.2, it has been possible to use the USB port for video transmission via the DisplayPort protocol, allowing to unify the video cables, power and data in a single USB Type-C cable.

The future of USB lies in the fourth generation

Version 4.0 of the standard will completely abandon the classic Type A form to be an improvement on Type C and again double the bandwidth up to 40 Gbits per second, in addition to being fully compatible not only with USB 3.2 standards. and 3.1 but also with Thunderbolt 3. Unsurprisingly, USB 4.0 is also the Thunderbolt 4 standard.

Another improvement is the fact that the new standard will be able to transmit data and video at the same time without sacrificing the transmit and receive channels of USB Type C based on versions 3.1 and 3.2 of the standard. This will allow the USB 4.0 standard to achieve the highest possible clock speed by combining video and data.

In addition, its charging power will be improved compared to USB 3.0, it is expected that in a few years we will say goodbye to the various types of proprietary power connectors that we use to charge our laptops.

Summary of USB generations and types and their bandwidth

Finally, we leave you a summary table on the different bandwidths of the USB port and which port variants support each generation.

And remember, the fact that a PC supports a USB generation does not mean that the peripherals do, if they are USB 1.1 if you connect them to a USB 2.0 port on the PC they will not go up to speed. of 2.0.