Every day we transfer a lot of data from our phone to our pen drives and from our computers to our hard disks. One thing that is common in all this data transfer is the presence of a data interface/ computer bus standard called USB. USB or Universal Serial Bus has made data/ power transfer across devices and accessories more convenient and is now the de-facto standard used by televisions, computers, laptops, cameras and smartphones.


In case you didn't know what a Computer Bus or Interface is, its simple. A Computer Bus is basically a path to transfer data within a computer (amongst its components) or other computers (and other devices).

Transferring data within a computer uses internal interfaces like PCIe, SATA, NVMe and SAS which are used in general for Hard Disks, Solid State Drives, Network Adapters and Graphics cards.

USB is a prime example of external interfaces used today. But did you know that USB is not the only external standard we use? You have Thunderbolt which was popularized by Apple with their MacBooks and Lightning for iPhones and iPads.

Let us now start by looking at the specifications of the most common of the data transfer standards

USB or Universal Serial Bus

USB was meant to act as a replacement to the whole plethora of ports that were at use to connect peripherals like printers, keyboards, mice, hard disks and more to the computer. USB aimed to standardize the port for all of these so that you had communication (data) and power supply.

What started in 1994 as a joint development by Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel yielded results in 1995 where a team which included Ajay Bhatt produced the first USB.

The reason why USB was needed was because the old Serial/ Parallel ports were simply too big, had crosstalk issues, were unreliable when a large data stream had to be transferred and were not durable enough due to their pin-based design.

USB meanwhile did not have such pins, was much smaller in size and could transfer data more reliably without interference.

USB being a standard has seen many versions starting with version 1.0 to the latest version USB 3.2.

Listed below are the different versions and their capabilities:

USB 1.0

  • Speeds of 12Mbps (Full Speed) and 1.5 Mbps (Low Speed)
  • Available in USB-A and USB-B connectors

USB 1.1

  • Speeds of 12Mbps (Full Speed) and 1.5 Mbps (Low Speed)
  • Available in USB-A and USB-B connectors
  • Version 1.1 of USB actually made it to the market as USB 1.0 had far too many issues

USB 2.0

  • Max Speed of 480Mbps (High Speed)
  • Available in USB-A, USB-B, USB Micro-A, USB Micro-B, USB Mini-A, USB Mini-B and USB Type-C connectors
  • Backwards compatible with USB 1.1
  • A power output of 5V at 0.5A (USB-A)

USB 3.0/ USB 3.1 Gen 1/ USB 3.2 Gen 1×1

  • Max Speed of 5 Gbps (Super Speed)
  • Available in USB-A, USB-B, USB Micro-B (3.0) and USB Type-C connectors
  • Backwards compatible with USB 1.1/ 2.0
  • A power output of 5V at 0.9A/1.5A (USB-A) and 5V at 3A (USB Type-C) 

USB 3.1/ USB 3.1 Gen 2/ USB 3.2 Gen 1×2/ USB 3.2 Gen 2×1

  • Max Speed of 10 Gbps (Super Speed+)
  • Has support for Thunderbolt, DisplayPort, MHL, HDMI, Ethernet, and audio functionality when used with USB Type-C connector
  • Available in USB-A, USB-B, USB Micro-B (3.0) and USB Type-C connectors
  • Backwards compatibility with ports other than USB Type-C risks losing the Power Delivery benefits and support for Thunderbolt, DisplayPort and other such additions
  • Backwards compatible with USB 1.1/ 2.0/ 3.0
  • A power output of 5V at 3A (USB Type-C) and up to 20V at 5A (USB Type-C with USB PD)

USB 3.2/ USB 3.2 Gen 2×2

  • Max Speed of 20 Gbps (Super Speed++)
  • Has support for Thunderbolt, DisplayPort, MHL, HDMI, Ethernet, and audio functionality when used with USB Type-C connector
  • A power output of 5V at 1.5A/ 3A (USB Type-C) and up to 20V at 5A (USB Type-C with USB PD)

USB connectors

USB connectors (Source: Wikipedia)

A little factoid for people who use external USB 3.0 HDD’s is that if you look at the micro-B connector on your HDD, it looks similar to the one shown in the image above (right side, USB 3.0-3.1). Now if for some reason you lose your cable and have nothing but your phones micro-B cable (left side, USB 1.0-2.0) cable with you, you can insert it to the HDD and use it at USB 2.0 speed.

While the USB Standards seems extremely complicated with multiple connectors and standards, it is being simplified with the new standards relying on the USB Type C as it helps not just with data transfers, but also allows for internet, video, audio and power delivery. If you look around you will see that most smartphones, laptops, computers, mp3 players, cameras come with the newer USB Type C connector and support for either USB 2.0, 3.0, or 3.1 (Gen 2).



A proprietary Apple innovation, the Lighting connector is reversible (like USB Type C) and was designed as the standard port for the iPhone, iPods and iPads.

Lightning connector

Lighting Connector (Source: Wikipedia)

When launched the Lighting connector used the data transfer speeds of USB 2.0 (480Mbps) and it received an upgrade in 2015 with the iPad Pro with the connector now using USB 3.1 Gen 1 (5Gbps).

Lighting also supports display (HDMI, DisplayPort) and audio (Digital) output when used with an adapter and the latest version Lighting on the iPhones also support USB-PD.

While the Lighting port was amongst the first to have reversibility, the much higher speeds of USB Type C (and USB 3.1 Gen 2 and 3.2) along with Thunderbolt support have made Apple to slowly ditch the Lighting connector for the USB Type C connector (iPad). It is only a short time before we get to see USB Type C on iPhones too.


Thunderbolt is a yet another interface developed by Apple and Intel as a rival to USB and was meant to carry data, video data and power through a single port. Designed as a connector for connecting peripherals to a computer, it did this by combining the PCIe, DisplayPort and Power supply. Ever since its inception, Thunderbolt has gone through three iterations as below:

Thunderbolt 1 (Light Peak)

  • A bandwidth of 10Gbps
  • Uses the Mini Display Port connector
  • Allows daisy chaining up to 6 devices
  • Doesn’t support 4K output

Thunderbolt 2 (Falcon Ridge)

  • A bandwidth of 20Gbps (Bi-directional)
  • Based on PCIe 2.0 and DisplayPort 1.2
  • Uses the Mini Display Port connector
  • Outputs video to a single 4K monitor at 60 Hz or dual QHD monitors
  • Allows daisy chaining up to 6 devices
  • Backwards compatible 

Thunderbolt 3 (Alpine Ridge)

  • A bandwidth of 40Gbps (Bi-directional)
  • Based on USB 3.1, PCIe 3.0, HDMI 2.0 and DisplayPort 1.2
  • Uses the USB Type-C connector
  • Outputs video to two 4K monitors at 60 Hz or a single external 4K display at 120 Hz or a 5K display at 60 Hz
  • Can use USB-PD for power up to 100 Watts
  • Allows connection to an external GPU and daisy chaining up to 6 devices
  • Backwards compatible when used with adapters

Thunderbolt 3 capabilty

Thunderbolt 3 capability

While Thunderbolt has remained the port of choice on the Macbook Air and Macbook Pro, Windows machines are slowly making use of it due to its higher bandwidth, support for DisplayPort, PCIe, USB Type C and USB-PD. That being said Thunderbolt is more expensive than regular USB and is one of the reasons why it hasn’t trickled down to more mid-range devices and is seen only on select high-end laptops.

Verdict and Summary

When it comes to the different external data transfer standards, USB is obviously the one with the widest reach due to its ubiquity and backwards compatibility. If your devices are up to date rarely will you need any adapters to use the latest USB standard This is one of the biggest reason for the success of USB.

The USB Type C standard isn’t the cleanest in terms of standard but it is surely getting there. The reason for the current mess today is with manufacturers pairing it up with the much older USB 2.0 standards and using non-USB-PD charging standards.

Apple’s Lighting port meanwhile has its merits when it comes to audio and usability but it a standard waiting to be killed off soon, as seen on the latest generation iPads.

That brings us to Thunderbolt which is clearly the future as it doesn’t really challenge any standard but embraces them all from USB, PCIe, DisplayPort and HDMI. Yes, it's not available in all the devices but any new technology takes time to be adopted.

Ultimately, what standard to use depends on your usage and the type of device you want to use. If you have read through our article on standards don’t forget to check out our next article on different connectors in use today. We did touch on that topic briefly here, but for a more in-depth read wait for our next piece.