DMS-59 Connector: Dual DVI Breakout Explained

The DMS-59 (Dual Monitor Solution, 59-pin) is a specialized video connector designed to support two digital or analog display outputs from a single low-profile interface. This article explains the design, functionality, and pin architecture of the DMS-59 connector, detailing how a standard breakout cable routes its internal signals into two independent DVI connections for multi-monitor setups.

What Is a DMS-59 Connector?

DMS-59 is an electrical connector primarily found on low-profile and business-oriented graphics cards, such as older NVIDIA Quadro and AMD FirePro models. Developed to overcome the physical space limitations of low-profile expansion slots, the connector provides the throughput of two separate video ports within the footprint of a single standard DVI port.

The connector features 59 pins arranged in four rows (a block of 15 pins, a block of 14 pins with one missing key pin to prevent incorrect insertion, and another two rows of 15 pins), along with grounding shielding.

How It Breaks Out into Two DVI Connections

Unlike standard display ports that require daisy-chaining (like DisplayPort MST) or active signal splitting, the DMS-59 interface inherently carries two fully independent video signal channels directly from the graphics processing unit (GPU).

The breakout process works through a passive "Y-cable" or adapter:

  1. Dedicated Pin Assignment: The 59 pins within the connector are physically divided between two display channels. One set of pins carries the Transition-Minimized Differential Signaling (TMDS) data channels, clock lines, and Display Data Channel (DDC) signals for Display 1, while a separate set carries the corresponding signals for Display 2.
  2. Passive Routing: Because the graphics card outputs two complete, separate DVI signals straight from the port, the breakout cable does not require an active converter chip or external power. The adapter functions purely as a mechanical wire router, mapping the internal pins of the DMS-59 plug directly to the standard pinouts of two individual DVI female receptacles.
  3. Signal Support: A DMS-59 to dual DVI breakout cable typically terminates in two DVI-I or DVI-D single-link connectors. Each output can independently transmit digital video up to a maximum resolution of 1920×1200 at 60 Hz per monitor. Because the DMS-59 connector also carries analog RGB signals, alternative breakout cables can split the connection into two VGA outputs or a combination of DVI and VGA.

By grouping two full sets of video pins into a single high-density housing, the DMS-59 interface allows compact desktop systems to drive two independent DVI monitors without requiring a secondary video card or larger PCIe brackets.