Extending the Topology


Based on point-to-point links, a HyperTransport chain may be extended into a fabric, using single and multi-link devices together. Devices defined for HT include:

  • Single HT link "cave" devices used to implement a peripheral function

  • Single or multi-link Bridges; (HT-to-HT, or HT to one or more other protocols such as PCI, PCI-X, AGP or Infiniband)

  • Multi-link Tunnel devices used to implement a function and extend a link to a neighboring device downstream, thus creating a chain

These devices are the basic building blocks for the HT fabric and are illustrated in Figure 2-11.

Figure 2-11. Basic HT Device Types

graphics/02fig11.jpg

Figure 2-12 exemplifies a HyperTransport topology that includes all three device types previously discussed. The basic difference between an HT-to-HT bridge and a tunnel device is:

  • A bridge creates a new link (with its own bus number), and acts as a HyperTransport host bridge for each secondary link.

  • A tunnel buffers signals, passes packets, but merely extends an existing link to another device. It is not a host, and the bus number is the same on both sides of the tunnel. It also implements an internal function of its own, which a bridge typically would not.

Figure 2-12. HyperTransport Topology Supporting All Three Major Device Types

graphics/02fig12.jpg



HyperTransport System Architecture
HyperTransportв„ў System Architecture
ISBN: 0321168453
EAN: 2147483647
Year: 2003
Pages: 182

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