What Is DAC Cable?_
Direct Attach Copper (DAC) is a passive or active copper cable assembly with transceivers pre-attached at both ends. DAC provides the lowest cost, lowest latency, and lowest power consumption for short-distance connections (up to 3m passive, 5m active at 400G). DAC is typically used for intra-rack connections from GPU servers to top-of-rack switches.
Technical Details
DAC cables are twinaxial copper assemblies with integrated QSFP-DD or OSFP connectors. Passive DAC uses no electronics and supports short distances (up to 3m at 400G), while active DAC includes signal conditioning circuits that extend reach to approximately 5m. DAC advantages include lowest latency (no optical conversion), lowest power consumption (passive DAC uses zero power), lowest cost per connection, and simplest installation (no transceiver configuration). The primary limitation is distance: for any connection exceeding 5m, AOC or fiber with discrete transceivers is required. In GPU racks, DAC is the preferred choice for server-to-TOR switch connections where distances are typically 1–3m.
How Leviathan Systems Works with DAC Cable
Leviathan Systems deploys DAC cables for intra-rack GPU server connections, selecting appropriate passive or active variants based on distance and speed requirements.