The **XAUI-RISER** is a specialized hardware component commonly used in high-performance networking equipment, server architectures, and telecommunications systems. Its primary function is to extend or adapt the **XAUI** (10 Gigabit Attachment Unit Interface) signals from a motherboard or backplane to an expansion card. --- ### 1. Core Technical Definition The XAUI interface is a standard for connecting 10 Gigabit Ethernet (10GbE) Media Access Control (MAC) layers to the Physical Layer (PHY). A riser card acts as a physical bridge, allowing for vertical or angled mounting of components to save space or bypass mechanical obstructions. ### 2. Key Electronic Components A XAUI-RISER typically consists of several critical electronic layers and parts: | Component Category | Specific Parts | Function | |:---|:---|:---| | **Differential Pairs** | Controlled Impedance Traces | Manages the 4-lane transmit (TX) and 4-lane receive (RX) signals at 3.125 Gbps per lane. | | **AC Coupling Caps** | Surface Mount Capacitors | Usually 100nF capacitors placed on high-speed lines to block DC voltage while allowing data signals. | | **Connectors** | High-Density Mezzanine or PCIe-style | Provides the physical mating interface between the riser and the host board. | | **EEPROM** | I2C Serial Memory | Stores board identification, revision data, and configuration parameters for the host OS. | | **Power Management** | LDO Regulators / Filters | Ensures clean power delivery to any active components or transceivers on the riser. | --- ### 3. Electronic Design Characteristics To ensure signal integrity over the 10GbE interface, the XAUI-RISER follows strict electronic design rules: * **Lane Alignment:** The interface uses 8 differential pairs (4 TX, 4 RX). The riser must maintain precise trace length matching between these pairs to prevent "skew." * **Differential Impedance:** Most XAUI designs require a differential impedance of **100 Ohms**. The PCB material (often FR4 or high-speed Megtron 6) is layered to maintain this. * **8b/10b Encoding Support:** While the encoding happens at the PHY level, the riser's physical path must be "clean" enough to support the 3.125 GHz signaling rate required by this encoding scheme. ### 4. Typical Applications * **Blade Servers:** Moving 10GbE signals from a horizontal motherboard to a vertical daughtercard. * **Network Switches:** Testing or extending XFP/SFP+ modules that utilize XAUI on the backend. * **Hardware Debugging:** Providing access points for logic analyzers to sniff 10GbE traffic. ---