MCX4621A-ACAB Mellanox ConnectX-4 25GbE 2 Ports SFP28 PCI-E 3.0 x8 Network Interface Card

Product Overview

The Mellanox MCX4621A-ACAB belongs to the renowned ConnectX-4 Lx EN family of Ethernet network interface cards, specifically engineered for high-performance, energy-efficient 25 Gigabit Ethernet connectivity. As a pivotal component within the broader category of OCP 3.0 mezzanine cards, this adapter delivers exceptional throughput, ultra-low latency, and advanced offloading capabilities.

Main Specifications

• Brand: Mellanox
• Model Number: MCX4621A-ACAB
• Product Type: 2 Ports Network Interface Card

Technical Highlights

• Compact plug-in card layout for seamless integration
• Total Number of Ports: 2
• Optimized for enterprise-grade server environments
• Supports Open Compute Project (OCP) 3.0 mezzanine standard
• PCIe 3.0 specification ensures reliable performance
• Dual-port setup with 10Gb Ethernet and 25Gb Ethernet SFP+
• Flexible deployment for diverse networking needs

Transmission Speed

• Maximum throughput of 25 Gigabits per second
• Stable wired connection for latency-sensitive workloads

Standards & Protocols

Compliance

• Fully aligned with OCP 3.0 standards
• Designed for compatibility across modern data centers

Supported Protocols

• 10 Gigabit Ethernet for mainstream enterprise traffic
• 25 Gigabit Ethernet for high-bandwidth applications

Performance Highlights

Efficiency

• Delivers consistent data transfer rates under heavy load
• Engineered for scalability in demanding IT infrastructures
• Stable wired connectivity minimizes packet loss
• Robust design ensures long-term operational durability

Ideal Use Cases

• Cloud computing environments requiring rapid data exchange
• Enterprise servers handling virtualization and storage traffic
• High-performance computing clusters with intensive workloads

Understanding of 2 Ports Network Interface Card

The Mellanox MCX4621A-ACAB ConnectX-4 Lx EN OCP 3.0 25GbE 2 Ports SFP28 PCI-E 3.0 x8 Network Interface Card represents an advanced Ethernet adapter engineered for high-performance data throughput, low latency packet processing, and enterprise-class reliability. Designed with a focus on hyperscale data center infrastructure, cloud computing platforms, storage networking environments, and virtualized workloads, this adapter integrates a highly optimized controller architecture capable of sustaining consistent multi-gigabit traffic without bottlenecks. Its OCP 3.0 compliant form factor allows direct compatibility with modern server chassis that require modular networking components capable of being deployed at scale while maintaining airflow efficiency and thermal balance.

PCI Express Interface Performance

The PCI Express 3.0 x8 host interface provides a high-bandwidth pathway between the network adapter and system motherboard. With theoretical bidirectional bandwidth exceeding 64 Gb/s, the PCIe interface ensures that the dual 25GbE ports can operate at full line rate simultaneously without bus saturation. The adapter’s internal DMA engines efficiently map memory buffers, enabling rapid packet transfers between system RAM and network interfaces. The PCIe architecture also supports advanced error reporting and reliability features that help maintain link stability under heavy I/O loads.

Dual 25GbE SFP28 Port Connectivity

This network interface card features two SFP28 ports designed for 25-gigabit Ethernet connectivity, offering flexible deployment across fiber or direct-attach copper cabling infrastructures. Each port is capable of independent operation, allowing administrators to configure redundancy, load balancing, or dedicated traffic segmentation. The SFP28 interface standard ensures compatibility with a wide range of optical modules and cables, making the adapter suitable for top-of-rack switching environments, storage fabric connections, and high-performance computing clusters.

Link Speed Negotiation and Compatibility

The ports support multiple link speeds including 25GbE and lower fallback speeds when connected to legacy infrastructure. Auto-negotiation functionality allows seamless integration into mixed-speed environments, while maintaining optimal signal integrity and minimal packet loss. The adapter automatically detects supported link parameters and adjusts internal transceiver settings to ensure stable communication across varying cable lengths and module types.

Signal Integrity and Physical Layer Enhancements

To maintain high data integrity at 25 gigabits per second, the adapter integrates advanced equalization algorithms and adaptive signal conditioning. These technologies compensate for attenuation, crosstalk, and electromagnetic interference, ensuring consistent packet delivery even in dense rack environments. The physical layer circuitry is optimized to reduce bit error rates and maintain stable transmission over extended operating durations.

Power Optimization

The card is engineered with efficient power distribution circuits that minimize electrical noise and maintain stable voltage levels across components. Thermal sensors continuously monitor temperature across critical regions of the board and adjust power states if necessary to prevent overheating. This design supports sustained full-rate performance without thermal throttling, even in high-density server installations.

OCP 3.0 Form Factor

The OCP 3.0 specification provides a standardized mechanical and electrical interface for modular network adapters within modern server platforms. The MCX4621A-ACAB adheres to this specification, ensuring compatibility with servers designed for Open Compute Project hardware ecosystems. The form factor allows tool-less installation and removal, simplifying maintenance procedures in large-scale deployments. Its layout is optimized for front-facing connectivity and airflow alignment, reducing cable congestion while maintaining efficient cooling.

OCP Mounting

The adapter’s PCB layout is engineered to meet OCP mechanical tolerances and structural stability requirements. Reinforced mounting points ensure secure installation, while precision edge connectors maintain reliable electrical contact with the host interface slot. The compact design allows deployment in high-density server trays without obstructing adjacent modules or airflow channels.

Airflow Alignment

Cooling efficiency is critical in data center hardware, and the OCP 3.0 orientation aligns the adapter’s heat-generating components with chassis airflow patterns. Strategic placement of heat-sensitive components allows incoming air to pass over controller and transceiver areas first, removing heat effectively and maintaining optimal operating temperatures across all subsystems.

Advanced Hardware Offload Capabilities

The ConnectX-4 Lx architecture includes multiple hardware offload engines that accelerate networking tasks typically handled by software. These offloads include TCP/UDP checksum calculation, IP header processing, segmentation offload, and receive-side scaling. By transferring these responsibilities to dedicated hardware logic, the adapter significantly reduces CPU utilization during heavy traffic conditions.

Virtualization Acceleration

Support for virtualization technologies allows the adapter to efficiently handle traffic for multiple virtual machines simultaneously. Hardware-assisted virtualization features enable direct assignment of virtual functions to guest operating systems, allowing each virtual machine to access network resources with minimal latency. This approach enhances performance consistency across virtualized workloads and ensures predictable throughput for cloud infrastructure deployments.

Latency Optimization

Low latency operation is a defining characteristic of this network interface card. The internal architecture minimizes packet traversal time through optimized pipelines and parallel processing paths. By reducing the number of clock cycles required for packet inspection and forwarding, the adapter delivers near-instantaneous response times for network transactions. This capability is particularly valuable for high-frequency data processing, clustered databases, and distributed computing environments where microsecond delays can affect application performance.

Adaptive Interrupt Moderation

The adapter dynamically adjusts interrupt frequency based on traffic intensity. During low traffic conditions, interrupts are generated immediately to minimize latency, while during high traffic bursts the system aggregates events to reduce interrupt overhead. This adaptive mechanism balances responsiveness with CPU efficiency, providing optimal performance under varying workloads.

Receive and Transmit Queue

Multiple hardware queues enable simultaneous packet processing streams, allowing parallel handling of network data. Receive-side scaling distributes incoming packets across processor cores, improving multi-threaded application performance. Transmit queues allow applications to send data concurrently without contention, ensuring smooth throughput even when multiple processes generate network traffic simultaneously.

Reliability and Error Handling

Enterprise networking environments require consistent reliability, and this adapter incorporates numerous safeguards to maintain stable operation. Error detection circuits monitor data paths and signal integrity, automatically correcting or retransmitting packets if anomalies are detected. The hardware includes advanced diagnostics capable of identifying link faults, cable issues, or module incompatibilities.

Firmware Stability

The adapter operates using a robust firmware architecture stored in non-volatile memory. Firmware routines manage initialization, link negotiation, and hardware configuration during system boot. Update capability allows administrators to apply enhancements or compatibility improvements without replacing hardware. The firmware environment is designed for stability, ensuring consistent performance across operating system environments and workloads.

Protection Against Data Corruption

Internal data buffers include parity checking and error detection logic to prevent corrupted packets from being transmitted or received. Memory protection mechanisms ensure that transient faults do not propagate through the system. These safeguards contribute to data integrity across mission-critical network transactions.

Power Efficiency and Consumption Profile

The MCX4621A-ACAB is engineered for high performance while maintaining efficient power usage. Dynamic power management circuits adjust voltage and frequency based on traffic load, reducing energy consumption during idle or low-utilization periods. This intelligent scaling helps data centers control operational costs and maintain thermal equilibrium across server racks.

Low-Power Idle States

When network activity decreases, the adapter transitions into low-power states that reduce internal clock speeds and disable non-essential circuits. These states are entered and exited seamlessly without interrupting network connectivity, ensuring that energy savings do not compromise performance readiness.

Efficiency Under Load

Even at full throughput, the adapter’s efficient silicon design minimizes wasted power by optimizing logic pathways and reducing unnecessary signal transitions. This efficiency ensures that the device delivers maximum data transfer capability while maintaining predictable thermal output.

Scalability Across Server Platforms

The OCP 3.0 form factor ensures compatibility with modern server platforms designed for modular networking. The adapter can be deployed across single-node systems, multi-node servers, and large cluster infrastructures without requiring hardware modification. This scalability makes it suitable for environments that demand consistent performance across hundreds or thousands of servers.

Use in Storage Networking Environments

High-speed Ethernet adapters are often used to connect servers to storage systems, and this model is optimized for such deployments. Its low latency characteristics and high throughput capabilities allow efficient transfer of large data blocks between compute nodes and storage arrays. Hardware offloads accelerate protocols used in storage communication, ensuring minimal overhead during sustained data transfers.

Throughput Stability for Large Data Transfers

The adapter maintains consistent bandwidth during prolonged transfers, preventing performance degradation over time. Buffer management algorithms prevent congestion and ensure smooth data flow even when multiple streams compete for resources. This stability is essential for applications that rely on uninterrupted access to large datasets.

High-Density Deployments

The compact architecture and efficient thermal profile of the MCX4621A-ACAB make it suitable for high-density server environments where multiple adapters operate in close proximity. Its low electromagnetic emissions and optimized airflow characteristics prevent interference between adjacent devices, maintaining stable operation even in densely populated racks.

Space Optimization

The slim OCP 3.0 layout allows the adapter to occupy minimal physical space while still delivering full dual-port 25GbE capability. This efficient use of space supports modern data centers that prioritize high compute density per rack.

Cooling Compatibility

The card’s thermal design ensures compatibility with both front-to-back and back-to-front airflow systems commonly used in enterprise servers. Heat-generating components are aligned with airflow channels so that cooling systems can remove heat efficiently without requiring additional fans or heatsinks.