How Many Pins Are in a DMS-59 Connector?

This article examines the pin configuration, physical design, and dual-display capabilities of the DMS-59 video connector. It details how the interface crams 59 pins into a compact form factor to drive two independent DVI or VGA monitors from a single graphics card slot, while exploring the specific pin layout and technical advantages that made this standard prevalent in enterprise hardware.

A DMS-59 (Dual Monitor Solution, 59 pins) connector contains exactly 59 pins. The physical interface features a 60-pin grid arranged in four rows of 15 pins each. However, pin 58 is intentionally omitted to act as a keying pin, preventing cables from being plugged in upside down and leaving a functional total of 59 pins crammed into a shell similar in size to a standard DVI port.

The primary function of this dense 59-pin arrangement is to deliver two full digital or analog video channels through a single port. A standard Single-Link DVI connection requires dedicated digital data channels, a clock signal, hot-plug detection, and I2C lines for display identification. Because a typical Single-Link DVI-D connector uses 18 to 24 pins, a graphics card would normally require two physically bulky ports to drive two monitors. By using 59 tightly grouped pins, a DMS-59 connector provides the necessary wiring to support two distinct Single-Link DVI-I channels simultaneously.

The 59-pin layout supplies:

• Two Single-Link DVI-D channels: Four transition-minimized differential signaling (TMDS) pairs per monitor (three color data pairs plus one clock pair), alongside dedicated display data channel (DDC) clock and data pins.
• Two Analog VGA channels: Red, green, blue, and horizontal/vertical synchronization signals for dual legacy analog outputs.
• Shared and isolated grounds: Multiple grounding pins clustered to shield high-frequency video signals from electromagnetic interference and cross-talk inside the compact connector housing.

To utilize these signals, systems connect a Y-shaped breakout cable or splitter to the DMS-59 port. The cable splits the 59 individual pins into two standard female DVI-I, DVI-D, or VGA connectors at the opposite end.

This design became an industry standard for low-profile, business-class graphics cards from manufacturers like NVIDIA and AMD. By packing 59 pins into the footprint of a single video port, hardware vendors could offer robust dual-monitor productivity on half-height PCI Express brackets used in small form factor desktop computers.