Users have long wanted desktop - level performance from a mobile computer. Thunderbolt was developed to create new user experiences by simultaneously supporting the fastest data and most video bandwidth available on a single cable, while also supplying power.
Thunderbolt allows users to connect to monitors that supports mini DisplayPort or DisplayPort connections. Adapters can allow for HDMI, DVI and VGA connections as well.
Thunderbolt 1 and 2 uses the same connector as MiniDisplayPort and Thunderbolt 3 uses USB Type C.
Thunderbolt 3 dynamically detects the capabilities of the cables and devices that are plugged in. Several modes can be detected and activated, in a way that is generally transparent.
USB Only Mode
If a USB device is plugged in, a USB Host controller inside the Thunderbolt 3 Enabled system is activated, and the Thunderbolt 3 silicon PHY drives USB (2.0 , 3.0 or 3.1 ) signals to the USB C port. In this mode, the thunderbolt 3 port behaves exactly like a typical USB 3 3.1 enabled connector.
DisplayPort Only Mode
If a DisplayPort Display or adapter is plugged in, the thunderbolt 3 enabled system will detect this and switch the pins driving the USB C connector to the DisplayPort alternate mode. Thunderbolt 3 silicon will then act as a router to send raw DisplayPort traffic from the graphics engine within the system out over the USB C connector pins, and pass that DisplayPort link directly to the display or adapter.
In this mode, a Thunderbolt 3 enabled USB C port will support a single four -lane (4 x5.4 Gbps , or HBR2 ) link of DisplayPort. These four links run across the two pairs of high speed wires in the USB-C connector and cable. This kind of DisplayPort link can support a single, uncompressed display at 4K resolution at 60 Hz.
DisplayPort and USB Mixed Mode
In this alternate mode of operation, one of the high speed connector pin pairs of signals will be dedicated to DisplayPort (now two lanes at 5.4 Gbps ) and one to USB 3.1. This allows for basic connectivity for data and display devices such as docking stations or data and display dongles.
With two lanes of DisplayPort 1.2a resolutions at Quad HD (QHD) can be achieved or 2560x1600 at 60Hz
Thunderbolt 3 Mode
If a cable and device supporting Thunderbolt are plugged in, the Thunderbolt silicon activates its highest capability mode, and links two bidirectional links at either 10Gbps or 20Gbps or 40Gbps.
Additionally, to fill this Thunderbolt link, the silicon extracts and routes up to four lanes of PCI Express Gen 3 ( 4 x 8 Gbps ) and up to two ( four lane ) full links of DisplayPort out over the Thunderbolt cable and connector to the device(s) attached downstream from the host system
Thunderbolt Networking Mode
An additional powerful capability of Thunderbolt allows to or more hosts to be connected directly ( or on separate ends of a Thunderbolt chain ) via Thunderbolt. In this case, Thunderbolt has software that creates an IP networking link between these systems.
This networking mode allows for the Thunderbolt interface to act as a virtual Ethernet adapter and transfer traffic over the PCI Express interface that the Thunderbolt silicon has in each host system.
Power Delivery and Charging
In each of the modes listed hereby, the Thunderbolt 3 system ( if designed to support this by the system manufacturer ) can also request to charge over the connector from a device or adapter designed for delivering power to the system up to 100W via the USB PD Specification.
In this way the Thunderbolt 3 enabled USB C Connector can support charging, display, data or all three at the same time in various configurations.