No one in their right mind can argue that the advent of USB was a bad thing. Before we first got the now iconic USB port, the world was filled with clunky, disparate connection standards.
The typical early 90s PC had LPT, serial, PS2, SCSI, and MIDI ports. To name a few! Now we have the Universal Serial Busbut it’s not as “universal” as you’d hope!
USB versions and speeds
It is important to understand that although two USB ports and cables may look are identical, it does not mean that they have the same capabilities. That’s because USB standards have improved over the years. The hardware that sends and receives information is faster and the internal wiring differs significantly.
Still, an important part of USB is the “universal” bit. In practice, this means that if a USB cable fits into a port, it will work. The worst that can happen is that it defaults to the oldest, slowest standard that both devices can understand. Which means some devices just don’t work properly because they can’t push the data through the cable fast enough.
When you buy a USB peripheral, it will tell you which is the highest standard it supports and – sometimes – requires. That means the computer, cable, and device must all conform to that particular USB standard in order for it to work as well as possible.
At the moment there are three generations of USB in the wild, with a fourth unreleased but in the works. Here’s the least you need to know:
- USB 1 has a maximum theoretical speed of 12 Mbps (megabits per second). These old devices will work with today’s modern USB, but at no more than that speed and usually a lower one. It is also called “Full Speed” USB, which can be confusing.
- USB 2 is way faster, with a maximum theoretical speed of 480 Mbps. The marketing name for USB 2 is “High Speed”.
- USB 3 is the most recent standard at the time of writing and has a theoretical speed of no less than 5 Gbps (gigabits per second). The marketing name is “SuperSpeed”.
USB 1.1 is actually the most widely used USB 1 standard, with virtually no USB 1.0 devices getting into users’ hands. USB 2.0 has had a few revisions, but USB 3 has had most of the revision work with USB 3.1 and 3.2.
These are further divided in generations. USB 3.1 has a Gen 1 and Gen 2 subdivision. USB 3.2 has Gen 1.2 and 2×2.
The generational versions are actually significantly different in performance. USB 3.1 Gen 1 runs at 5 Gbps, but Gen 2 doubles that! The USB 3.2 generations run at 5.10 and 20 Gbps respectively.
A Note on Thunderbolt 3 over USB-C
Lightning Strike 3 is an entirely different standard for data transfer than USB. However, it uses the same USB-C port! This isn’t as confusing as it sounds, so let’s break down what you need to know:
- Any USB-C device will work in any Thunderbolt 3 port.
- A Thunderbolt device will not work in a regular USB-C port without Thunderbolt.
- Thunderbolt USB-C ports often have a small image of a lightning bolt next to them.
- USB-C cables work like Thunderbolt cables, but cheap cables may not hold speed well.
- Thunderbolt cables also work as USB-C cables.
Thunderbolt is a nice technology, but this article is about USB, so we’ll leave it at that.
Types of USB ports
Now that we’ve covered the different USB generations, let’s talk about the actual physical ports. Before we do that though, here’s a quick tip – USB 3 ports are conventional blue inside! That makes it easy to distinguish them from older USB port types.
The original USB port is known as the Type A port. This is the port type we all know and love, and can be found on everything from flat screen TVs to clock radios. USB 1 and USB 2 Type-A ports have only four pins internally. Two for data and two for power. USB 3 Type-A ports have a total of nine pins, but are fully backwards compatible.
Next we have the less common Type B port. These are usually seen on devices such as printers or external hard drives. It is a female port for devices that are not “host devices” such as a computer. Type B USB 1 and 2 ports are: not physically compatible with USB 3 Type-B ports.
Finally, we have the latest Type-C port. This small, tightly wired port is reversible. Which means, unlike Type A or B ports, you can place it anywhere. With an adapter, it is compatible with all USB except USB 1. It replaces other connection types from USB 3.2 and later.
That’s it for the so-called “standard” ports, but there are “mini” and “micro” versions of these for devices that are too small to handle full-sized USB-A ports. Game controllers, smartphones, and other small devices can have mini and micro versions of Type-A and Type-B ports. There are also Type-AB ports for devices that act as both hosts and peripherals.
Before USB-C ports, smartphones usually had Micro-B ports. Mini-B ports can be found on devices such as the PlayStation 3 controller.
While Micro-B ports are still widely used for smartphones, power banks and most modern small electronic devices, USB-C is quickly becoming the new standard for each device that uses USB, regardless of size.
USB power standards
USB is more than just a way to transfer data between devices. It is also a way of transferring power. With the exception of Apple’s mobile devices, just about every modern smartphone uses some kind of USB port for both charging and data.
Many devices that don’t transfer data at all still use USB to charge. An example are power banks to small toy drones. Some USB cables carry power only, without the data transfer wiring. Power cables that come with power banks are sometimes of this type.
It is actually quite useful to use a power-only cable to avoid virus infections of mobile devices. For example at airports where chargers may be present, hackers can swap them with malware-infected devices. A so-called “data blockerUSB cable prevents that particular exploit.
In terms of the actual power coming through a USB cable, there is a lot of variability. One thing you should know, however, is that if you plug a USB device into a USB-compatible port, it will only draw as much power as it needs or as much power as the port can supply, whichever is lower.
So you don’t have to worry about connecting your phone to a charger with a higher power than the charger. As long as both devices and the cable are from reputable manufacturers, you don’t have to think about that.
What is important to know is that some USB power sources cannot properly charge or power your device. USB provides power according to the generation of the hardware. USB 1.0 and 2.0 provide 500 mAh of power. USB 3.0 can give up to 900 mAh of juice. USB 3.1 can deliver a whopping 3000 mAh (3A)!
These are simply the numbers a manufacturer must meet in order to meet the certification minimums. You’ve probably noticed that car chargers and Apple iPad chargers are often rated at 2.1A, which isn’t part of a USB specification. To make use of the extra power available, the device has to talk to the charger to negotiate how much power it wants.
If not, it defaults to the minimum, which is usually 500 mAh. All you need to know is that the charger and device must both support the same “fast charging” power standard which must be carried over USB specifications.
Apart from the high power delivery of the latest USB 3 versions, all other fast charging standards are not industry standard. So there is no guarantee that your “fast charging” smartphone will be optimally charged on a third party charger.
For example, on Android phones, there is usually a notification letting you know if the device is charging slow or fast, along with an estimated time.
Using USB on Macs
USB has been a feature of Apple computers for almost as long as USB itself has been around. The first iMac in 1998 did away with all but two USB ports and two FireWire ports. It’s no exaggeration to say that Apple has played a big part in USB adoption.
Modern Macs have also done something radical when it comes to USB technology, doing away with ALL ports in exchange for one or two USB-C ports. This means that if you want to use a device that doesn’t natively use USB-C, the only solution is a USB-C hub.
The good news is that USB-C has so much bandwidth and power that adding a cheap hub device can give you any connection you want. Make sure to look for one that has been specifically tested for Mac compatibility. MacBooks with two USB-C ports can work with so-called “dual-hub” devices, which plug into both USB-C ports and combine them for use with the hub.
A final note on USB 4″
Before closing the book on USB, let’s talk briefly about the future. USB 4 is coming, so it’s a good idea to be somewhat prepared for it. This new standard supports up to 40 Gbps bandwidth, but is only backwards compatible with USB 3.2 and USB 2.0.
In practice, this probably won’t bother anyone, as all USB 1 hardware is already essentially obsolete. The current USB-C port will be the mainstay of USB 4 and so all USB will be unified, eliminating concerns about whether different ports will work together. So in a few years you won’t have to remember anything you read in this article.