INTEGRATED 10/100/1000M/2.5G ETHERNET CONTROLLER FOR PCI EXPRESS APPLICATIONS (Supports Realtek Dragon SW for bandwidth control)

General Description

The Realtek RTL8125BG/RTL8125BGS 10/100/1000M/2.5G Ethernet controller combines a four-speed IEEE 802.3 compatible Media Access Controller (MAC) with a four-speed Ethernet transceiver, PCI Express bus controller, and embedded memory. With state-of-the-art DSP technology and mixed-mode signal technology, the RTL8125BG/RTL8125BGS offers high-speed transmission over CAT 5e UTP cable or CAT 3 UTP (10Mbps only) cable. Functions such as Crossover Detection and Auto-Correction, polarity correction, adaptive equalization, cross-talk cancellation, echo cancellation, timing recovery, and error correction are implemented to provide robust transmission and reception capability at high speeds. The RTL8125BGS provides a built-in switching regulator.

The RTL8125BG/RTL8125BGS supports the PCI Express 2.1 bus interface for host communications with power management, and is compatible with the IEEE 802.3u specification for 10/100Mbps Ethernet, the IEEE 802.3ab specification for 1000Mbps Ethernet and the IEEE 802.3bz specification for 2500Mbps Ethernet. It supports an auxiliary power auto-detect function and will auto-configure related bits of the PCI power management registers in PCI configuration space.

Advanced Configuration Power management Interface (ACPI)—power management for modern operating systems that are capable of Operating System-directed Power Management (OSPM)—is supported to achieve the most efficient power management possible. PCI MSI (Message Signaled Interrupt) and MSI-X are also supported.

In addition to the ACPI feature, remote wake-up (including AMD Magic Packet and Microsoft Wake-Up Frame) is supported in both ACPI and APM (Advanced Power Management) environments. To support WOL from a deep power down state (e.g., D3cold, i.e., main power is off and only auxiliary exists), the auxiliary power source must be able to provide the needed power for the RTL8125BG/RTL8125BGS. To further reduce power consumption, the RTL8125BG/RTL8125BGS also supports PCIe L1 substate L1.1 and L1.2.

The RTL8125BG/RTL8125BGS supports ‘RealWoW!’ technology that enables remote wake-up of a sleeping PC through the Internet. This feature allows PCs to reduce power consumption by remaining in low power sleeping state until needed.

Note: The ‘RealWoW!’ service requires registration on first time use.

The RTL8125BG/RTL8125BGS supports Protocol offload. It offloads some of the most common protocols to NIC hardware in order to prevent spurious Wake-Up and further reduce power consumption. The RTL8125BG/RTL8125BGS can offload ARP (IPv4) and NS (IPv6) protocols while in the D3 power saving state.

The RTL8125BG/RTL8125BGS supports the ECMA (European Computer Manufacturers Association) proxy for sleeping hosts standard. The standard specifies maintenance of network connectivity and presence via proxies in order to extend the sleep duration of higher-powered hosts. It handles some network tasks on behalf of the host, allowing the host to remain in sleep mode for longer periods. Required and optional behavior of an operating proxy includes generating reply packets, ignoring packets, and waking the host.

The RTL8125BG/RTL8125BGS supports IEEE 1588, IEEE 1588-2008, and IEEE 802.1AS, also known as Precision Time Protocol (PTP). IEEE 802.1AS is part of the Ethernet AVB (Audio Video Bridging) standard. PTP provides micro-second level accuracy time synchronization among multiple Ethernet devices. The RTL8125BG/RTL8125BGS implements hardware support for these standards. The RTL8125BG/RTL8125BGS supports IEEE 802.1Qav, also part of the Ethernet AVB standard. IEEE 802.1Qav is a forwarding and queuing mechanism enhancement. It provides guarantees for time-sensitive (i.e., bounded latency and delivery variation), loss-sensitive real-time audio video (AV) data traffic transmissions.

The RTL8125BG/RTL8125BGS supports IEEE 802.3az-2010, also known as Energy Efficient Ethernet (EEE). IEEE 802.3az-2010 operates with the IEEE 802.3 Media Access Control (MAC) Sublayer to support operation in Low Power Idle mode. When the Ethernet network is in low link utilization, EEE allows systems on both sides of the link to save power.

The RTL8125BG/RTL8125BGS is compatible with Microsoft NDIS5, NDIS6 (IPv4, IPv6, TCP, UDP) Checksum and Segmentation Task-offload (Large send and Giant send) features, and supports IEEE 802.1P Layer 2 priority encoding and IEEE 802.1Q Virtual bridged Local Area Network (VLAN) and IEEE 802.1ad Double VLAN. The above features contribute to lowering CPU utilization, especially benefiting performance when in operation on a network server.

The RTL8125BG/RTL8125BGS supports Receive-Side Scaling (RSS) to hash incoming TCP connections and load-balance received data processing across multiple CPUs. RSS improves the number of transactions per second and number of connections per second, for increased network throughput.

The maximum supported jumbo frame length of the RTL8125BG/RTL8125BGS is 16384 bytes

The device features inter-connect PCI Express technology. PCI Express is a high-bandwidth, low-pin-count, serial, interconnect technology that offers significant improvements in performance over conventional PCI and also maintains software compatibility with existing PCI infrastructure.

The RTL8125BG/RTL8125BGS is suitable for multiple market segments and emerging applications, such as desktop, mobile, workstation, server, communications platforms, and embedded applications.



  • Integrated 10M BASE-Te and 100/1000M/2.5G BASE-T 802.3 compatible transceiver
  • Supports 2.5G Lite (1G data rate) mode
  • Auto-Negotiation with Extended Next Page capability (XNP)
  • Compatible with NBASE-TTM Alliance PHY Specification
  • Supports PCI Express 2.1
  • Supports pair swap/polarity/skew correction
  • Configurable MDI port ordering (MDI swap) for easy PCB layout
  • Crossover Detection & Auto-Correction
  • Supports 1-Lane 2.5/5Gbps PCI Express Bus
  • Embedded OTP memory can replace external EEPROM
  • Supports hardware ECC (Error Correction Code) function
  • Supports hardware CRC (Cyclic Redundancy Check) function
  • Transmit/Receive on-chip buffer support
  • Supports PCI MSI (Message Signaled Interrupt) and MSI-X
  • Supports 25MHz Crystal / External Oscillator
  • Built-in switching regulator (RTL8125BGS only)
  • Generate reference clock from Crystal
  • Supports power down/link down power saving/PHY disable mode
  • LAN disable with GPIO pin
  • Customized LEDs
  • Controllable LED Blinking Frequency and Duty Cycle
  • Self-Loopback diagnostic capability
  • Thermal management
  • 48-pin QFN ‘Green’ package
  • Serial EEPROM
  • Supports 32Mbytes External Serial Peripheral Interface (SPI) Flash
  • Supports ECMA-393 ProxZzzy Standard for sleeping hosts
  • Supports LTR (Latency Tolerance Reporting)
  • Wake-On-LAN and ‘RealWoW!’ Technology (remote wake-up) support
  • Supports 32-set 128-byte Wake-Up Frame pattern exact matching
  • Supports Microsoft WPI (Wake Packet Indication)
  • Supports PCIe L1 substate L1.1and L1.2


  • Compatible with IEEE 802.3, IEEE 802.3u, IEEE 802.3ab
  • Supports IEEE 1588v1, IEEE 1588v2, IEEE 802.1AS time synchronization
  • Supports IEEE 802.1Qav credit-based shaper algorithm
  • Supports IEEE 802.1P Layer 2 Priority Encoding
  • Supports IEEE 802.1Q VLAN tagging
  • Supports IEEE 802.1ad Double VLAN
  • Supports IEEE 802.3az (Energy Efficient Ethernet)
  • Supports IEEE 802.3bz (2.5GBase-T)
  • Supports Full Duplex flow control (IEEE 802.3x)

Software Offload

  • Microsoft NDIS5, NDIS6 Checksum Offload (IPv4, IPv6, TCP, UDP) and Segmentation Task-offload (Large send v1 and Large send v2) support
  • Supports jumbo frame to 16K bytes
  • Supports quad core Receive-Side Scaling (RSS)
  • Supports Protocol Offload (ARP & NS)

Realtek Dragon Software

  • Smart Auto Adjust Bandwidth Control
  • Visual User Friendly UI
  • Visual Network Usage Statistics
  • Optimized Default Setting for Game, Browser, and Streaming Modes
  • User Customized Priority Control


  • PCI Express 10/100/1000/2500M Ethernet on Motherboard, Notebook, or Embedded systems.