Currently, there are three Thunderbolt generations available, simply called 1, 2, and 3.
The first Thunderbolt connection has four 5.4 Gbps DisplayPort channels, two used for data transmission and two used for data reception, thus generating one 10 Gbps transmission channel and one 10 Gbps reception channel. Thunderbolt 2 doubles the transfer rate by allowing the four channels to be joined in the same direction. Functionally, the first two generations are identical, and both make use of mini DisplayPort (mini DP) connectors.
The third generation, however, brought some important new features. Besides doubling the bandwidth in relation to the previous generation, by doubling the number of DisplayPort channels available and using the PCI Express 3.0 standard, it supports USB 3.1 connection and makes use of the type C USB connector instead of the mini DisplayPort. Therefore, Thunderbolt 3 connections are compatible with USB 3.1 devices. However, when connected to USB 3.1 devices, the Thunderbolt connection is limited to 10 Gbps (1 GB/s), which is the maximum transfer rate of the USB 3.1 bus. Additionally, Thunderbolt 3 allows the creation of 10G Ethernet networks and is able to provide up to 100 W without an external power supply.
The first two Thunderbolt versions allow up to seven devices per port, while the third version the maximum number of devices per port was reduced to six. It is possible to use up to two video monitors at the same time.
|Generation||Maximum bandwidth (Gbps)||Maximum bandwidth (GB/s)||Devices||Compatibility|
|1||10 Gbps||1 GB/s||7||PCIe 2.0 x4, DP 1.1a x4|
|2||20 Gbps||2 GB/s||7||PCIe 2.0 x4, DP 1.2 x4|
|3||40 Gbps||4 GB/s||6||PCIe 3.0 x4, DP 1.2 x8, USB 3.1, 10G Ethernet|
Thunderbolt 3 is still compatible with DisplayPort, but since now it uses a different connector type, an adapter is required. Because of the higher available bandwidth, it is possible to connect up to two 4K (4096 x 2160 x 30 bits) at 60 Hz video monitors, one 4K at 120 Hz video monitor, or one 5K (5120 x 2800 x 30 bits) at 60 Hz video monitor using a Thunderbolt 3 connection.