USB Speed Comparison: From USB 1.0 to USB4

Connectivity between devices via cables is taken for granted in today’s world, but before 1995 it was a tedious task. Universal Serial Bus came to the fore with an industry standard serial interface designed to establish connectivity between various hardware devices and peripherals without much hassle. It was developed with the aim of replacing numerous cable connectors that were previously required to connect external devices into personal computers or PCs.

With a pre-configured smaller form factor and ensuring compatibility, USB created a standardized interface for all major devices saving time and money instead of different devices having designated ports and connectors or interfaces which overtime became ineffective for efficient work. Such ports like the PS/2 and serial port were exclusive to some peripherals and was time consuming in configuration. Seven companies began development of the USB in around 1995. People can be thankful to Ajay Bhatt and his team working at Intel to successfully integrate the first circuits supporting USB that year. Later in May 1996, USBs came to production at the commercial level. Now USB is very common, such as USB data cable, USB flash, laptop, even in car.

USB 1.0

Before the version 1.0, there were numerous versions tested out by several companies with the first USB protocol being version 0.7 by Intel, Microsoft, IBM, Compaq and others till 1994. The iterations continued with USB version 0.8, 0.9, 0.99 and 1.0 for the next two years. But it did not lead to any functional products.

In 1995, the USB-IF organization was formed by these companies. At that time, the USB 1.0 had a data transfer rate of 1.5Mbps (Megabits per second) which was referred as Low Speed and a maximum output current of 5V/500mA. That was the best iteration they produced at that time and yet, not many manufacturers were buying into it. In fact, very few and it did not sell well.

The sweet spot was discovered in USB version 1.1, a revised iteration of USB 1.0, released by USB-IF in 1998. A transfer rate of 12Mbps (unusually referred as Full Speed) appeared to be satisfying configurations for the manufacturers to produce and utilize the standard at scale. So USB 1.1 was the first major breakthrough, basically for its transfer speed.

Interesting enough, USB 1.0 was renamed as USB 2.0 Low Speed and USB 1.1 was renamed as USB 2.0 FullSpeed. This lead to the category of USB 2 Speeds and the updated USB 2.0.

USB 2.0

USB 2.0 came to the fore in the year 2000, the turn of the millennium. It was certified as USB 2.0 HiSpeed becoming popular for quick connectivity. It has a transfer rate of 480Mbps with a maximum output current of 5V/500mA. The emergence of USB 2.0 outpaced its predecessor, 1.0. They became outdated and in a short period, were quickly phased out.

USB 2.0 still exists to this day and is the oldest living USB standard currently. Many card readers like the one pictured below still uses USB 2.0 standard. For reference, these card readers were manufactured several years after the release of USB 2.0 and still sells to this day.

USB 2.0 is also popular for Embedded Systems, microcontroller boards and development kits for research purposes. Many manufacturers of Development kits utilize this USB standard to create their products and sell them at scale as the 480 Mbps transfer rate specification is good enough for Software programming and code compilation. The following test runs on Machine Learning algorithms and Embedded Systems were performed with devices using the USB 2.0 standard.

480 Mbps is equal to 60 MB/s, thus allowing for a lot of sampling for data collection as seen in the following Gyroscope test using an Embedded device with a gyroscope sensor under USB 2.0 standard. The test run was for 60 seconds.

So why do some companies still develop their products under the USB 2.0 standard? Because it is efficient for some experimentations and applications like the ones mentioned above and is cost effective to produce. The following is a standard chart on the evolution of USB versions and their speeds.

USB Speed Comparison Chart

Standard	Also Known As	Logo	Year Introduced	Connector Types	Max. Data Transfer Speed	Cable Max Length
USB 1.1	Full Speed USB		1998	USB A USB B	12 Mbps	300cm
USB 2.0	Hi-Speed USB		2000	USB A USB B USB Micro A USB Micro B USB Mini A USB Mini B USB C	480 Mbps	500cm
USB 3.0	USB 3.1 Gen 1 USB 3.2 Gen 1 SuperSpeed		2008 (USB 3.0) 2013 (USB 3.1)	USB A USB B USB Micro B USB C	5 Gbps	300cm
USB 3.1	USB 3.1 Gen 2 USB 3.2 Gen 2 SuperSpeed+ SuperSpeed 10Gbps		2013 (USB 3.1)	USB A USB B USB Micro B USB C	10 Gbps	300cm
USB 3.2	USB 3.2 Gen 2×2 SuperSpeed 20Gbps		2017 (USB 3.2)	USB C	20 Gbps	300cm
USB4 20Gbps	USB4 Gen 2×2		2019	USB C	20 Gbps	80cm
USB4 40Gbps	USB4 Gen 3×2		2019	USB C	40 Gbps	80cm

USB 3.0

USB 3.0 was released in 2008 and came with a multitude of sub-versions. Each new sub-version release update defined its speed. It was from this version that USB transfer speeds breached the Gbps (Gigabits per second) barrier. It was built on top of the form factor of USB 2.0, with a total of 9 pins; first row of 4 pins for USB 2.0 and the second row of 5 pins designed specifically for USB 3.0. This schematic makes the 3.0 backwards compatible with USB 2.0 ports.

USB 3.1 / USB 3.2

The two sub-versions (or speeds) of USB 3.0 are respectively USB 3.1 (also named as USB 3.1/USB 3.2 Gen 1) and USB 3.2 (also named as USB 3.1/USB 3.2 Gen 2). These versions were released between 2013 and 2014. USB 3.2 Gen 2×2 was a more updated version released in 2017. With every update, the transfer speed kept rising from 5 Gbps to 10 Gbps to 20 Gbps. The cable length requirements became shorter to 3 meters. Being shorter than USB 2.0 (5 meters max. length), it has faster transmission speed. It was also compatible with various USB port types. All these spec updates were leading to the build up of USB 4.0.

USB Color Codes for Differnet Versions

Internal Port	Color	USB Version
	White	USB 1.0
	Black	USB 2.0
	Blue	USB 3.0
	Yellow	USB 2.0/USB 3.0
	Green/Teal	USB 3.1
	Red	USB 3.2/USB4

Note: There is no precise color code, but the most general color codes defined for USB versions are perceived in the above table.

USB 4.0

USB 4.0 came to the forefront in 2019, after significant advancements to USB 3.2. With a data transfer rate of 20 Gbps (Gen 2×2) to 40 Gbps (Gen 3×2) and cable lengths reduced to a mere 0.8 meters; the version 4.0 far outranks its predecessors. USB 4.0 is backwards compatible with USB 3.2 and USB 2.0. Although it has been introduced to the market in recent times, it seems the USB evolution is not stopping anytime soon.

USB Data Transfer Rate Comparative Analysis

A graphical comparative analysis of every released USB versions and their data transfer speeds is shown below.

From the above column graph, it is understood that the USB data transfer rate started very slowly in the Mbps range between versions 1.0 and 2.0, but then exponentially increasing in the Gbps ranges with version 3.0 and the succeeding updates at the end of the 2000s decade.

USB 2.0 VS USB 3.0 Comparison

A sample test run was performed using two USB storage drives, version 2.0 and 3.0, to determine their duration of transferring data, i.e. data transfer speed. They were tested to see how fast they can send and receive a 540 MB video file. After performing the tests, the following results regarding duration were obtained in the data table.

USB Version / File Transfer Condition	Receiving File (Minutes:Seconds.milliseconds)	Sending File (Minutes:Seconds.milliseconds)
USB 2.0	02:08.26	00:20.71
USB 3.0	00:19.86	00:06.55

To clarify, transferring the file from the laptop to the USB storage drive was the receiving test and vice-versa, file transfer from the USB storage to the laptop was the sending test. From the tests, it is clear that for the higher speed, USB 3.0 takes a shorter time period to either send or receive data compared to USB 2.0. Cable lengths, copper wire thickness, material type can also impact the data transfer rate. The comparisons for these two USBs don’t just end there. More factors bring about the Pros and Cons of both these versions.

USB 2.0 Pros

• Compatible with multiple USB connector types, the most by any version as of now.
• Low Current consumption (500 mA).
• Cheaper cost of production for its minimal specs.
• USB Drivers available even with the most modern devices and software systems.
• Micro and Mini USB connector types were introduced during this version.
• USB 2.0 form factor laid the foundation for the development of USB 3.0.
• Efficient for programming and compiling codes.
• Oldest USB standard existing as of today since its release (22 years).

USB 2.0 Cons

• Data transfer rate is slow, takes more time to send or receive files.
• Sometimes it needs the specific USB 2.0 port to connect, depending on the device.
• Cable length is maximum 5 meters long for proper transfer, anything more decreases the speed.

USB 3.0 Pros

• Fast Data Transfer starting at 5 Gbps, takes short time.
• Getting faster with each new sub-version release.
• Functional even with shorter cable length, i.e. 3 meters.
• USB 3.1 led to the creation of USB Type-C in 2014.
• Backwards compatible with USB 2.0.

USB 3.0 Cons

• High current consumption (starts from 900 mA).
• Compatible with fewer connector types compared to USB 2.0.
• Complex design meaning higher cost to manufacture.

Summary

Universal Serial Bus was a proposed standard that took years to iterate and needed a collective effort from various tech companies to simplify the connectivity we know today. For a novel concept, it did fail initially at the production level. But after USB 2.0, it revolutionized the way we carry our data, the way we can transfer data from one device to another. USB started slow but then gradually took off with speed after 2008. With every new version, it demonstrated reliability and overtime, data transfer was taken for granted without any issues. And the evolution of USB is not stopping anytime soon. USB 2.0 and USB 3.0 will seem to co-exist for now. USB 4.0 is eying to the future.