Universal Serial Bus, short USB, is actually a pretty easy Port.
Yet there are, depending on the type of application, several cable endings that deliver different transfer speeds. All that leads to the relatively new USB-Port Type-C, who can support non-USB-Protocols in alternative mode, such as power supply (up to 100 watts), DisplayPort, MHL, HDMI, VGA or Thunderbolt.
To combat the evolving chaos, especially regarding the names, I want to bring some light into the dark.
It all started in 1996 with USB 1.0, which was revised in 1998 with USB 1.1 and enabled a transfer of data with 12 Mbit/s (gross). USB 2.0 was presented in 2000, with a speed of 480 Mbit (gross). In 2008 USB 3.0 followed and made it possible to transfer data with 5 Gbit / s (gross), thus becoming the new state of the art.
Around Mid/End 2013 the denomination USB 3.0 disappeared on many devices. From then on it was USB 3.1. What’s up with that? What happened? What are the differences?
To answer these questions, I want to take a look at the different stages of expansion respectively cable(endings)/plugs/connectors and ports of USB.
USB Type-A is known since the beginning of USB and can be found in 99% of all computers (the host, so to say). This type is compatible with USB 1.0, 2.0 and 3.0 – it is being offered in the variants Standard, Mini (USB 1.0/2.0 only) and Micro (USB 1.0/2.0 only).
USB Type-B can be found on the devices to be connected; for example printers, external hard drives and smartphones. This type is compatible to USB 1.0, 2.0 and 3.0 as well – it is being offered in the variants Standard, Mini (USB 1.0/2.0 only) and Micro. Due to more pins, the plugs for USB 3.0 look a little wider than those for USB 1.0/2.0.
USB Type-C ist the newest shit. As you can see in the upper graphic, there is only one connector, which is universally and usable from both ends. Besides the before mentioned non-USB-protocols it is downward compatible to all other USB-protocols.
But let’s get back to our questions about the difference between USB 3.0 and 3.1.
First of all: There are two variants of USB 3.1; Generation 1 and Generation 2… because why make things simple…
USB 3.1 Gen 1 is just the regular USB 3.0 Standard with 5 Gbit/s gross data transfer rate; it was just renamed.
USB 3.1 Gen 2 is the new Type-C, that has a new, uniform and universal usable port compared to Gen 1, and double the transfer speed with now 10 Gbit/s (gross).
Problems with USB Type-C
Despite this relatively easy constellation, the problem lies within the almost endless chaos of available attachments of USB-C.
Not every cable, port or power adapter is fully compatible to the specifications of Type-C. There are just to many combinations that have to be considered, so that only the newest hardware like the Apple MacBook Pro (Late 2016) covers most of them. Old hardware with a USB-C port. like the regular MacBook (early 2016) supports, despite the Type-C port, only the old USB 3.0 Standard, including the slow data transfer rate.
But it gets worse. Many USB-C peripheral devices are limited as well. Just think about the USB-C HDMI adapter. Which method of implementing was used here? HDMI through USB 3.0? The alternative mode with native HDMI? It could also be (multiplexed) HDMI through Thunderbolt. Same problem here, that only the newest hardware supports all methods of implementing. So it can easily happen, that an adapter works great on computer X but fails to work on computer Y.
The last problem relates to cables. Unfortunately there exists a huge variety of quality and compatibility. Many cables only support data rates up to 5 Gbit/s, the USB 3.1 Gen 1 specification. Other cables are not suitable for loading or refuse to work when using the alternative mode with Thunderbolt.
So when buying cables and adapters, one has to be extremely careful and take a closer look of the specifications. Otherwise you don’t have to wonder why something doesn’t work or in the worst case, why hardware got damaged.
USB-C vs. Thunderbolt 3
The real confusion about the USB-C port starts in combination with Thunderbolt 3.
While Thunderbolt 1 and Thunderbolt 2 used the Mini DisplayPort connector to transfer data, Thunderbolt 3 uses USB-C.
Again, there are a lot of surprises here.
It all starts with not every USB-C port being compatible to TB3. Prime example again is the normal MacBook (Early 2016), whose USB-C port does not support TB3… Only the ports of new MacBook Pro have full TB3 support. It all depends on the hardware being used…
Furthermore you need special (short active) cables for TB3, that look exactly the same as a normal USB-C cable. Otherwise, the anticipated transfer rate of 40 Gbit/s can’t be reached and (depending on the cable) due to downward compatibility, you can only use USB 3.1 Gen1 or USB 3.1 Gen2. So you have to be extremely careful here as well, to avoid an unwanted surprise.