HP Z1 G2 Technical White Paper page 16

Technical white paper | HP Z1 G2 Workstation
Protocol architecture
Thunderbolt technology is based on a switched fabric architecture with full-duplex links. Unlike bus-based I/O
architectures, each Thunderbolt port on a computer is capable of providing the full bandwidth of the link in both
directions with no sharing of bandwidth between ports or between upstream and downstream directions. The
Thunderbolt protocol architecture can be abstracted into four layers as shown in Figure 5.
Figure 5. Thunderbolt Technology Architecture
A Thunderbolt connector provides dual protocol bi-directional 20Gbps of bandwidth enabling the connection to
Thunderbolt products or to DisplayPort devices. Compatibility to DisplayPort devices is provided by an interoperability
mode between host graphics controllers and DisplayPort products. If a DisplayPort device is detected, the Thunderbolt
controller will drive compatibility mode DisplayPort signals to that device (e.g. native DisplayPort signaling). Support for
DisplayPort also enables easy connectivity to other display types, such as HDMI, DVI or VGA with an adapter.
Thunderbolt cables may be electrical or optical; both use the same Thunderbolt connector. An active electrical cable can
be used for connection up to 3 meters in length and can provide up to 10W of power delivered to a bus-powered device.
An active optical cable would be used for connections greater than 3 meters in length and up to 100 meters in length.
Optical cables do not provide power for bus powered devices.
The Thunderbolt protocol physical layer is responsible for the link maintenance including hot-plug detection and data
encoding. The physical layer introduces minimal overhead and provides a full 20Gbps per channel of usable bandwidth to
the upper protocol layers. The Thunderbolt protocol architecture transport layer includes a high performance, low-power
switching architecture, a highly efficient, low-overhead packet format with flexible QoS (Quality of Service) support that
allows multiplexing of bursty PCI Express transactions with isochronous DisplayPort communications on the same link.
DisplayPort and PCI Express protocols are mapped onto the transport layer. The mapping function is provided by a
protocol adapter which is responsible for the efficient encapsulation of the mapped protocol information into transport
layer packets. Mapped protocol packets between a source device and a destination device may be routed over a path that
may cross multiple Thunderbolt controllers. At the destination device, a protocol adapter recreates the mapped protocol
in its native format. The advantage of protocol mapping in this way is that Thunderbolt technology enabled devices
appear as PCI Express or DisplayPort devices to the operating system enabling the use of standard drivers.
Controller architecture
A Thunderbolt controller is the building block used to create Thunderbolt products. The Thunderbolt controller contains
a high performance cross bar Thunderbolt protocol switch, up to two Thunderbolt ports, up to two DisplayPort protocol
adapter ports, and a PCI Express switch. A Thunderbolt controller acts as a junction in a daisy chain of Thunderbolt
products, as well as a point of entry and an exit point for the encapsulated interconnect protocols (PCI Express and
DisplayPort).
The host Thunderbolt controller is responsible for managing the connections in the Thunderbolt daisy chain, plug
events, and wake events. The Thunderbolt controller high performance cross bar switch routes traffic in the converged
I/O domain between the PCI Express input, the multiple DisplayPort inputs and the multiple output channels. The high
performance crossbar distributes packets to the protocol mapping engines or the downstream ports enabling maximum
flexibility.
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Application specific
Protocol Stacks
PCle DisplayPort
Common Transport Layer
Electrical/Optical Layer
Connector and Cable
Thunderbolt technology
TM
HP recommends Windows.