NVIDIA ConnectX‑8 C8180 vs C8240: Selecting the Right SuperNIC for AI and HPC
Jan 26, 20261 min read
With the rapid advancement of AI and HPC workloads, the continuous growth in GPU computing capability places higher demands on data center network performance, particularly in large-scale, multi-node deployments. To sustain efficient GPU-to-GPU communication and minimize data movement overhead, network infrastructure must evolve in parallel with compute architectures. NVIDIA ConnectX-8 SuperNIC emerges in this context as a next-generation smart NIC designed for ultra-high-bandwidth and low-latency environments. By delivering up to 800Gb/s of throughput, it addresses the growing pressure on network fabrics in modern AI clusters.
This article compares two ConnectX-8 NIC variants that share the same hardware and software platform but differ in port configuration and speed options. By focusing on these practical differences, it aims to help customers understand how each model fits different deployment scenarios and make more informed selection decisions.
How ConnectX‑8 Accelerate AI Networking?
FS NVIDIA® ConnectX-8 SuperNIC is designed to address the networking demands of large-scale AI and HPC systems, where bandwidth, latency, and efficiency must scale together. Supporting both InfiniBand and Ethernet at speeds of up to 800Gb/s, ConnectX-8 provides a unified, high-performance networking foundation for modern AI fabrics.
Built on PCIe Gen6 with up to 48 lanes, ConnectX-8 enables high host-to-NIC throughput and consistent low-latency communication. Across all variants, it supports a common set of advanced networking capabilities, including RDMA and RoCE acceleration, GPUDirect RDMA and GPUDirect Storage, programmable congestion control, and in-network computing technologies such as NVIDIA SHARP for InfiniBand environments.
These capabilities allow critical data paths—such as collective communication, synchronization traffic, and storage access—to be handled efficiently by the NIC, reducing host overhead and improving overall system utilization. As a result, ConnectX-8 SuperNICs deliver consistent performance, scalability, and efficiency across different form factors and port configurations, forming a common architectural foundation for next-generation AI data centers.
Detailed Comparison of C8180 and C8240
The NVIDIA ConnectX-8 SuperNIC portfolio includes multiple variants designed to address different system architectures and deployment requirements. While the ConnectX-8 SuperNIC portfolio is built on a unified architecture, NVIDIA offers multiple variants with different port form factors, link configurations, and system integration options to address diverse deployment requirements.
Among these variants, C8180 and C8240 represent two mainstream configurations commonly used in large-scale AI and HPC systems. The primary differences between them are reflected in port form factors, supported link speeds, and how the NIC integrates with the host and surrounding devices. Understanding these distinctions helps align network design with system topology and workload characteristics. The table below highlights the specifications of C8180 and C8240.
Feature |  |  |
Form Factor | PCIe Half Height, Half Length 2.69 × 6.58 in (68.50 × 168.40 mm) | PCIe Half Height, Half Length 2.61 × 6.62 in (66.40 × 168.40 mm) |
PCIe Interface | Gen6 SERDES @ 64GT/s, x16 lanes (Gen5 compatible) | Gen6 SERDES @ 64GT/s, x16 lanes (Gen5 compatible) |
Networking Ports | Single OSFP cage, InfiniBand & Ethernet | Dual-port QSFP112, InfiniBand & Ethernet |
InfiniBand Data Rate | XDR/NDR/HDR/HDR100/EDR/SDR | NDR/HDR/HDR100/EDR/SDR |
Ethernet Data Rate | 400/200/100 Gb/s | 400/200/100 Gb/s |
Capabilities | Secure Boot Enabled, Crypto Enabled with x16 PCIe extension option | With x16 PCIe Socket Direct extension option, Secure Boot Enabled, Crypto Enabled |
LEDs Scheme | Two LEDs: LED1 is a bi-color LED (Yellow and Green) LED2 is a single-color LED (Green)  | One Bi-Color LED: There is one bi-color (Yellow and Green) I/O LED per port that indicates port speed and link status.  |
Maximum Trace Length on the Board | 75mm (2.95 inch) | 140mm (5.51 inch) |
How Should I Choose Between ConnectX-8 C8180 and C8240?
When selecting between the NVIDIA ConnectX‑8 SuperNIC models C8180 (900‑9X81E‑00EX‑ST0) and C8240 (900‑9X81Q‑00CN‑ST0), understanding the fundamental hardware and port configuration differences is critical for aligning with deployment needs. These differences influence how each model performs in high‑performance computing (HPC), artificial intelligence (AI) clusters, and high‑capacity Ethernet networking in modern data centers.
1. Port Configuration
The C8180 features a single OSFP module that, in its default configuration, provides a single InfiniBand port supporting XDR at up to 800Gb/s. Through the port‑splitting feature, the OSFP interface can be reconfigured into two 400GbE Ethernet ports or up to eight 100 GbE ports, offering flexibility across various link granularities and segmentation needs. Meanwhile, the C8240’s dual QSFP112 ports default to two 400GbE Ethernet ports, with support for splitting into up to eight 100 GbE ports when finer partitioning is required.
This architectural distinction results in different topological use cases:
C8180’s OSFP with XDR InfiniBand is ideal where a very high single‑link throughput is needed (e.g., 800Gb/s InfiniBand fabrics or large RDMA data flows).
C8240’s dual QSFP112 provides built‑in dual‑link connectivity for standard 400GbE networking or paired InfiniBand links without requiring further configuration.
2. InfiniBand Bandwidth
InfiniBand support differs between the models. C8180’s default configuration supports XDR (800Gb/s) in addition to NDR and HDR data rates, while C8240 supports NDR and HDR protocols by default. XDR enables peak InfiniBand throughput, which can be beneficial in HPC or GPU‑cluster fabrics where link bandwidth directly affects inter‑node communication latency and performance.
3. Form Factor
Though both cards share a PCIe Gen6 x16 interface & Secure Boot/Crypto capabilities, they differ in physical profile: the C8180 is slightly wider, whereas the C8240 has a slightly narrower footprint with a longer PCB trace length. This can affect chassis compatibility and signal routing in densely populated server boards. The specifications document highlights these form factor differences.
4. Manageability
The C8180 uses two LEDs per port (one bi-color, one single-color), providing more detailed status indicators for speed, link state, and error conditions. C8180’s dual LED scheme gives more granular feedback, beneficial for diagnostics or environments requiring detailed port monitoring.
The C8240 employs one bi-color LED per port, offering a simplified, per-port view of link speed and status. C8240’s single per-port LED is well-suited for dual-port or multi-port rack deployments, providing clear and intuitive operational visibility.
Deployment Scenarios
Select C8180 when:
High single-link InfiniBand throughput (XDR up to 800Gb/s) is required, such as in ultra-dense compute clusters or RDMA-intensive storage fabrics.
Flexible port splitting is needed (e.g., 1×800Gb/s, 2×400GbE, or 8×100 GbE endpoints from a single physical module).
Workloads prioritize maximum per-link performance rather than total port count.
Select C8240 when:
Standardized dual 400GbE or dual NDR/HDR InfiniBand links are required, for example in top-of-rack (ToR) integration or dual-homed architectures.
Redundancy or link aggregation across two independent ports is a priority.
Operational visibility with clear per-port status indicators benefits large-scale deployments.
Conclusion
C8180 and C8240 are built on the same ConnectX‑8 platform, offering high-performance networking for AI and HPC workloads. Choosing the right variant depends on deployment needs, whether for maximum single-link throughput or dual-link redundancy.
As an authorized NVIDIA and Mellanox partner since August 2022, FS provides complete networking solutions and expert technical support to help enterprises optimize their AI and HPC clusters. Explore our ConnectX‑8 solutions today to maximize performance and efficiency.