DAC (Direct Attach Cable) is widely used for short-distance, high-speed interconnects in data centers, connecting servers, switches, and storage devices with low latency and minimal power consumption.

Overview of DAC Cables

A Direct Attach Cable (DAC) is a factory-terminated high-speed cable assembly with integrated connectors at both ends, transmitting electrical signals directly over copper conductors without optical conversion . DAC cables are cost-effective, energy-efficient, and ideal for short-range connections, typically within a single rack or between adjacent racks in data centers . They are available in passive and active types:

• Passive DAC: Relies solely on copper wiring, suitable for distances up to 5 meters, with nearly zero latency and minimal power consumption .
• Active DAC: Incorporates signal conditioning electronics such as Redriver or Retimer chips to extend reach up to 10–15 meters while maintaining signal integrity .

Key Applications

DAC cables are primarily used in high-speed data center interconnects, including:

• Server-to-switch connections: Directly linking servers to top-of-rack or leaf switches for 10G, 25G, 40G, 50G, 100G, or higher speeds .
• Switch-to-switch connections: Short-range interconnects between switches within the same rack or adjacent racks, supporting high-density networking .
• Storage area networks (SANs): Connecting storage devices to servers or switches for low-latency data access .
• High-performance computing (HPC) clusters: Providing ultra-low latency links for compute nodes in AI, machine learning, and scientific computing environments .

Advantages

• Low latency and power consumption: Passive DACs consume no additional power and introduce minimal signal delay .
• Cost-effective: Eliminates the need for separate transceivers and fiber, reducing hardware and operational costs .
• Ease of deployment: Factory-terminated assemblies simplify installation and reduce potential points of failure .
• High signal integrity: Active DACs (ACC and AEC) use Redriver or Retimer chips to compensate for signal loss, enabling longer distances while maintaining high-speed performance .

Comparison with Other High-Speed Cables

• ACC (Active Copper Cable): Adds a Redriver chip at the receiver end to amplify and equalize signals, extending DAC reach beyond passive limits .
• AEC (Active Electrical Cable): Uses Retimer chips at both ends to reshape and recondition signals, suitable for higher data rates and longer distances .
• AOC (Active Optical Cable): Fiber-based solution with integrated optics, offering longer reach and reduced electromagnetic interference, but at higher cost .

Typical Deployment Scenarios

• Intra-rack connections: Passive DACs for distances ≤5 meters.
• Adjacent rack connections: Active DACs (ACC or AEC) for distances up to 10–15 meters.
• High-density AI or HPC fabrics: Active DACs or AOCs for ultra-high-speed links with minimal latency . In summary, DAC cables are essential for short-range, high-speed interconnects in modern data centers, offering a balance of performance, cost, and energy efficiency, with active variants extending their applicability to longer distances and higher data rates.