PCI Express® External Cabling • Host Side Adapter

Most computer systems are based on the PCI Express® standard as a high speed backbone for interconnection of peripheral components with a host CPU. Typically all PCI Express® based devices are located closely in a common enclosure.
The PCI-SIG PCI Express® External Cabling Specification addresses extended applications, such as split-systems or I/O expansion by means of a suitable copper cable, available e.g. for a x 4 PCI Express® link, up to 7m length. When used with an AOC (Active Optical Cable), distances of up to 300m can be bridged between host and target systems.

Coupling systems by PCI Express® is a solution which allows significantly more throughput and lower latency compared e.g. to 1 or 10 Gigabit Ethernet. Thus, remote target systems become a genuine part of the host. The DC2-STAG is a XMC style mezzanine card, designed for dual PCIe x 4 external cabling (host system adapter). The board is provided with two PCIe x 4 front panel connectors, for attachment of one or two remote target systems via PCI Express®.
For optimum performance, the DC2-STAG requires a PCIe x 8 Gen2 capable XMC carrier board. This would allow both cabling connectors to be operated simultaneously with PCIe Gen2 speed, at full throughput. For typical applications, a PCIe x 4 based XMC carrier may be also adequate.

The on-board PCIe Gen2 packet switch splits the upstream link into two equal downstream links (x 4), each delivering up to 20GT/s to an associated target system. Dual clocking is provided on the DC2-STAG, for usage of optical cables (AOC) in a SSC host system.

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XMC Overview


  • Form factor XMC single-width mezzanine card 139mm x 74mm
  • Stack height 10mm XMC to host
  • Host I/F connector P15 XMC (option XMC 2.0)
  • x 8 or x 4 PCI Express® 2.0 (5.0 Gbps)
  • +3.3V only operated (VPWR not in use)

Simplified Block Diagram

dc2 blk
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