What Is the Difference Between SST and MST in DisplayPort?
DisplayPort connections handle multi-monitor setups using two primary transport modes: Single-Stream Transport (SST) and Multi-Stream Transport (MST). The fundamental difference between them lies in how video data travels across a single cable: SST transmits only one video stream, causing connected external displays to mirror the same image, whereas MST splits total interface bandwidth across multiple independent video streams, enabling extended desktops and daisy-chaining from a single port.
Understanding Single-Stream Transport (SST)
Single-Stream Transport is the original transmission mode introduced with the DisplayPort 1.0 standard. Under SST, the source device transmits a single, unified stream of audio and video across the link.
Because SST carries only one display data packet at a time, any secondary monitors connected through an SST hub or downstream port receive the exact same video feed. This results in mirrored displays rather than an expanded workspace. SST requires lower processing overhead from graphics drivers and hardware controllers, making it universally supported across modern operating systems, including Windows, macOS, ChromeOS, and Linux.
Understanding Multi-Stream Transport (MST)
Introduced with DisplayPort 1.2, Multi-Stream Transport multiplexes multiple independent video streams into a single physical connection. The receiving hardware—either an MST-enabled monitor or an MST distribution hub—demultiplexes this single high-speed data path into individual streams routed to respective screens.
MST unlocks two primary setup options:
- Daisy-Chaining: A computer connects to Monitor 1 via DisplayPort In; Monitor 1 then connects to Monitor 2 via DisplayPort Out using a single chain.
- MST Hubs and Docks: A single DisplayPort or USB-C connection from a computer routes to an external hub, which splits the signal into multiple DisplayPort or HDMI outputs displaying independent content.
Key Differences
| Feature | Single-Stream Transport (SST) | Multi-Stream Transport (MST) |
|---|---|---|
| Introduced In | DisplayPort 1.0 | DisplayPort 1.2 |
| Stream Capacity | 1 video stream per port | Multiple independent streams per port |
| Multi-Display Mode | Mirrored / Cloned only | Extended desktop or Mirrored |
| Daisy-Chaining | Not supported for extended desktops | Fully supported |
| Bandwidth Management | Full link bandwidth dedicated to 1 stream | Shared across all connected displays |
| Hardware Overhead | Minimal | Requires MST-compliant controllers |
Bandwidth and Resolution Limits in MST
While MST allows multiple independent monitors on one cable, all displays must share the total physical bandwidth of the host's DisplayPort version.
For instance, a standard DisplayPort 1.4 connection provides approximately 25.92 Gbps of usable data bandwidth. If a user connects two 4K displays running at 60 Hz without compression, the required data throughput exceeds the single-port limit. In such cases, the system must either:
- Lower refresh rates (e.g., dropping to 30 Hz).
- Reduce resolution on downstream screens.
- Utilize Display Stream Compression (DSC) to compress video streams visually losslessly if supported by both the GPU and monitors.
Operating System Compatibility
Hardware compatibility does not guarantee MST functionality because operating system driver stacks handle DisplayPort streams differently.
Windows and most Linux distributions natively support MST, allowing multi-monitor daisy-chains and multi-display USB-C docks out of the box.
In contrast, macOS does not support MST for display extension. When an Apple Mac connects to an MST hub or daisy-chained DisplayPort configuration, the operating system defaults to SST mode, resulting in duplicated or mirrored screens across all connected downstream displays. Mac users requiring multiple independent external monitors typically rely on Thunderbolt docks or individual display connections to separate host ports.