The **M2REB-S4D-R2** is a specific model of an **M.2 Expansion Board** (often referred to as a "Riser" or "Bridge" board), typically utilized in industrial computing, embedded systems, or high-end server chassis to redirect M.2 signals. --- ## 1. Technical Specifications The part number indicates a specific physical and electrical configuration. Below is a breakdown of its primary electronic characteristics: | Feature | Specification | | :--- | :--- | | **Interface Type** | M.2 (NGFF) | | **Keying** | Typically M-Key (for NVMe) or B+M Key | | **Bus Protocol** | PCIe Gen 3.0 / Gen 4.0 (Backwards compatible) | | **Connectivity** | S4D (Standard 4-Lane Differential) / R2 (Revision 2) | | **Mounting Type** | Horizontal or Vertical (Specific to chassis) | --- ## 2. Key Electronic Components This board is more than just a physical adapter; it contains specific circuitry to ensure signal integrity over the distance of the riser: ### A. Signal Re-drivers / Retimers Because M.2 signals (PCIe) are high-frequency, long traces can lead to data loss. This board often includes: * **Differential Pair Routing:** Carefully matched trace lengths to prevent phase shifts. * **Impedance Control:** Traces are designed at 85-100 ohms to match PCIe standards. ### B. Power Management Circuitry M.2 drives require stable **3.3V** power. The board includes: * **Decoupling Capacitors:** Small SMD capacitors (typically 0.1µF to 10µF) located near the connector to filter out high-frequency noise. * **Power Plane:** A dedicated copper layer within the PCB to handle the current demands of high-performance NVMe SSDs. ### C. Physical Connectors * **Gold Fingers:** Hard gold plating on the edge connector to withstand multiple insertion cycles. * **SMT M.2 Slot:** A surface-mount connector designed to secure the SSD with a screw or clip. --- ## 3. Application Use-Case This part is commonly found in **1U/2U Rackmount Servers** where space is limited. 1. **Orientation Change:** It allows the SSD to sit parallel to the motherboard to save vertical height. 2. **Modular Upgrades:** Allows manufacturers to add M.2 support to motherboards that only have proprietary expansion headers. 3. **Thermal Management:** By moving the SSD away from the CPU, it allows for better airflow around the storage device. --- ## 4. Hardware Connectivity ```text Motherboard Slot (PCIe/M.2) <---> M2REB-S4D-R2 Bridge <---> NVMe SSD ``` *Note: Ensure the BIOS supports "Bifurcation" if this riser is being used to split one x8 slot into two x4 M.2 slots.* ---