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The Computer Interconnect, or CI, is a radial computer bus developed by the DIGITAL Equipment Corporation. It was the first interconnect used for OpenVMS Cluster communications. The CI supports the exchange of information among VAX and Alpha nodes, and HSC and HSJ nodes at the rate of 70 megabits per second on two paths.

An OpenVMS Cluster system based on the CI for cluster communications uses star couplers as common connection points for computers connected in a radial configuration, and HSC and HSJ subsystems. Workstations can be added to a CI OpenVMS Cluster system using an additional type of interconnect, such as Ethernet or FDDI, in the configuration - they are typically configured as satellite nodes.

The CI supports a maximum bandwidth of 70 Mbps per channel and two channels. The maximum number of nodes that can be connected to a star coupler is 32: up to 16 nodes can be OpenVMS systems, the rest HSJ and HSC storage controllers. The number of star couplers is limited by the number of CI adapters.

Hardware Support

The following systems support CI interconnect:

  • AlphaServer 8400, 8200
  • AlphaServer 4100, 2100, 2000
  • DEC 7000/10000
  • VAX 6000/7000/10000