USB Type-C and Thunderbolt 3: a port to slave them

Universal Serial bus, short USB, is actually a fairly simple port.

However, depending on the purpose of the application, there are various cable ends which also provide different transmission speeds. The whole thing is currently in the relatively new USB port type-C, which in alternative mode also supports non-USB protocols like a power supply (up to 100 watts), DisplayPort, MHL, HDMI, VGA or Thunderbolt.

In order to become a master of this now-created chaos, especially as far as the naming is concerned, I would like to do some clarification.

Overview of protocols

It started in 1996 with USB 1.0, which was revised in 1998 with USB 1.1 and allows the transmission of data at 12 Mbit/s (gross). In the year 2000, USB 2.0 was introduced, which transmits data at 480 Mbit (gross). USB 3.0 followed in November 2008 and at that time was the new top rider with a transmission speed of 5 Gbit/s (gross).

Since about mid/late 2013, however, the name USB 3.0 has disappeared for many devices. Henceforth, USB 3.1 is the most common speech. What is this? What happened? Where are the differences?

Cable (ends)/Stecker/Buchsen/Ports at a glance

To answer these questions, I would like to take a look at the different expansion stages or cable (ends)/Stecker/Buchsen/Ports of USB.

USB Type-A is known since the beginnings of USB and can be found in 99% of all computers (quasi the host). This type is compatible with USB 1.0, 2.0 and 3.0 and is available in standard, Mini (USB 1.0/2.0 only) and micro (USB 1.0/2.0 only) variants.

USB Type-B can be found on the devices to be connected; such as printers, external hard drives, or smartphones. This type is also compatible with USB 1.0, 2.0 and 3.0 and is offered in the standard, Mini (only for USB 1.0/2.0) and micro variants. Due to the additional pins, however, the plugs for USB 3.0 look slightly wider/thicker than they are in USB 1.0/2.0.

USB Type-C is now the latest hot shit. As you can see in the graph above, there is only one connector that can be used on both sides and universally. In addition to the above mentioned non-USB protocols, there is, of course, backward compatibility with all other USB protocols.

But back to our initial issues about the difference between USB 3.0 and 3.1.

First of all: USB 3.1 is available in two variants; Generation 1 and Generation 2… why keep things simple…

Behind USB 3.1 Gen 1, the normal USB 3.0 standard with 5 Gbit/s gross data transfer rate is hidden; It was just a renaming.

With USB 3.1 Gen 2, the new type-C is meant to be a completely new, uniform and universally usable port compared to Gen 1, as well as a speed doubling to 10 Gbit/s (gross).

In summary:

Problems with USB Type-C

Despite this fairly simple constellation, the sheer infinity of the available accessories is probably the biggest problem of USB-C.

Not every cable, port or power supply is fully compatible with the type-C specification. There are simply too many combinations that need to be taken into account, so that most of the time only current hardware such as Apple’s new MacBook Pro (late 2016) covers many of these combinations. Older hardware with a USB-C port, such as the normal MacBook (early 2016), supports only the old USB 3.0 standard, including the lower data transfer rate, despite the type-C port.

It’s going to be even worse. Many USB-C peripheral devices are also limited. I’m just thinking of a USB-C HDMI adapter. Which method of implementation is used here? HDMI via USB 3.0? The alternative mode with native HDMI? It could also be (multiplexed) HDMI via Thunderbolt. Here, too, only very current hardware supports all methods of possible implementations. Therefore, it is quite possible that an adapter works wonderfully at computer X; Computer y fails to serve.

The last problem concerns the cables. Unfortunately, there are very different qualities and compatibilities here. Many cables only support data transfer rates up to 5 Gbit/s, which corresponds to the USB 3.1 Gen 1 specification. Other cables are not suitable for charging or deny the service when using alternate mode with Thunderbolt.

You have to be extremely careful when purchasing cables and adapters and look closely at their specifications. Otherwise, you should not be surprised if something does not work or if, in the worst case, your hardware is damaged.

USB-C vs. Thunderbolt 3

The USB-C port is really confusing, but only in connection with Thunderbolt 3.

While Thunderbolt 1 and Thunderbolt 2 use the Mini DisplayPort port to transfer data, Thunderbolt 3 sets to USB-C.

Again, a lot of surprises are waiting.

It starts with the fact that not every USB-C port is compatible with TB3. Best example here is the normal MacBook (early 2016), whose USB-C port TB3 does not support… Only the ports of the new MacBook Pro offer full TB3 support. So it comes back to the hardware used…

You also need special (short active) cables for TB3, which look exactly like a normal USB-C cable. Otherwise, the provided data transfer rate of 40 Gbit/S is not reached and one drops (cable dependent) due to the backward compatibility of TB3 on USB 3.1 Gen 1 or USB 3.1 Gen 2. Therefore, you also have to be extremely careful which cable you use to avoid nasty surprises.