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TXO Systems

Direct attach cables (DAC)

Direct attach cable, also known as DAC, is a cable assembly of various lengths. The DAC has integrated connector modules at either end; commonly SFP+, XFP or QSFP+. They use the Twinax format, which is the same as coax but with dual conductors instead of single.

DAC cables are used as a transmission medium for short reach interconnection applications in the data centre where high bit rates are required. For example between servers, switches and storage. In addition they can be found in inter-rack and intra-rack applications in the data centre.

The DAC plugs into the same port as ordinary transceivers and they support Ethernet and Fibre Channel (FC). They are popular because they offer cost savings and also power savings compared to alternatives and as such are widely used in data centres globally.


Active or Passive DAC?

Passive and active cables of this type appear visually the same. However, there are a number of important differences. Generally the passive cables operate over short distances and are “dumb” (i.e. all they can do is tell the switch what brand they are and that is it). The passive cable consumes no power and is seen by the switch or device as a transparent transmission medium. This means that they do not have a chip inside the SFP connector to boost the performance of the cable as with the active cable. This chip generally performs signal boosting and equalisation which means that the active cable can be longer (e.g. 5M or more) and it can perform certain active functions that previously took place inside the switch.

TXO provides both active and passive cables to the desired length. Commonly requested products are 10 Gigabit Ethernet twinax cables in either active or passive forms with SFP+ housing each end. Direct attach copper (DAC) is a very popular choice for 10G ethernet for reaches up to 10M for reasons of both low latency and low cost.


TXO’s Direct Attach Cables: Fast Facts

  • TXO offers a wide range of active and passive direct attach cable assemblies
  • Available in a range of form factors and lengths
  • Significant cost savings compared with OEM supply
  • Transparent quoting process
  • Stock holding in USA and Europe for rapid delivery anywhere in the world
  • Tested in host system before dispatch
  • Backed by a comprehensive 3 year advance replacement warranty
  • The use of compatible direct attach cables does NOT void equipment warranty