540-BCOS: Dell Mellanox ConnectX-5 Dual Port 25GbE SFP28 PCIe Adapter

Also listed as: 023R5D, 23R5D, MCX512A-ACAT · made by NVIDIA

The Dell 540-BCOS is a Dell Mellanox ConnectX-5 Dual Port 25GbE SFP28 PCIe Adapter delivering 25GbE network connectivity across 2x 25GbE SFP28 via PCIe 3.0 x16 / PCIe 4.0 x8. Built with NVIDIA controller architecture, the 540-BCOS provides hardware offload acceleration and virtualization support for R740, R740XD, R640, R750 enterprise servers.

Specifications

About the 540-BCOS

The Dell 540-BCOS is a Dell Mellanox ConnectX-5 Dual Port 25GbE SFP28 PCIe Adapter engineered to deliver 25GbE network transmission across 2x 25GbE SFP28 over PCIe 3.0 x16 / PCIe 4.0 x8. Powered by NVIDIA controller architecture on the 540-BCOS, it executes hardware-level protocol processing, RoCE, and SR-IOV virtualization while maintaining a thermal envelope of approximately 14W. In Dell's networking portfolio, 540-BCOS provides dedicated high-bandwidth fabric connectivity for clustered virtualization, network storage, and enterprise database hosts.

Compatibility

Engineered for Dell PowerEdge servers including R740, R740XD, R640, R750, the 540-BCOS mounts directly into FHHL / LPHL PCIe Adapter locations. The 540-BCOS installs into a standard PCIe 3.0 x16 / PCIe 4.0 x8 expansion riser slot with matching bracket profile. Cabling the 540-BCOS requires 25GbE-rated media, including direct attach copper twinaxial assemblies, optical transceivers, or patch leads matched to its physical ports. Supported operating systems on the 540-BCOS include VMware ESXi, Red Hat Enterprise Linux, and Windows Server with native Dell drivers.

How to identify a genuine unit

Authentic Dell 540-BCOS units carry an identification label displaying DP/N 023R5D and NVIDIA model code MCX512A-ACAT along with Dell regulatory marks. In iDRAC Network Devices inventory, the card registers under part number 540-BCOS with active link state, port MAC addresses, negotiated speed, and certified Dell firmware. Onboard physical indicators on the 540-BCOS provide link status and port activity monitoring.

Buying used

When purchasing a pre-owned 540-BCOS, examine the gold edge connector fingers for scratches, peeling contacts, or missing surface-mount capacitors. Ensure that the 540-BCOS PCIe mounting bracket (low-profile or full-height) is intact and properly aligned for chassis installation. Validate in iDRAC Lifecycle Controller that the 540-BCOS is recognized with certified Dell firmware and passes diagnostics under sustained 25GbE network traffic.

Fits these models

• Dell PowerEdge R740
• Dell PowerEdge R740xd
• Dell PowerEdge R640
• Dell PowerEdge R750
• Dell PowerEdge R650

Works together

How the Dell 540-BCOS connects to servers, storage and the network: 3 ways, with the hardware on each path.

Plan and size it

• Draw this setup in the topology planner mrplanb.com
• Add up rack power and space rack-density.com
• iSCSI explained mrplanb.com
• Virtualization storage Ledger: scored storage platforms mrplanb.com
• Network monitoring tools compared mrplanb.com
• Dell E-Lab Navigator (Dell interoperability) dell.com

Equivalent part numbers

• NVIDIA MCX512A-ACAT NVIDIA ConnectX-5 EN Dual-Port 25GbE SFP28 PCIe 3.0 x8 Low-Profile Ethernet Network Adapter NVIDIA Mellanox ConnectX-5 EN 25GbE Dual-Port SFP28 PCIe Adapter OEM base

FAQ

Sources

• Dell Mellanox ConnectX-5 Dual Port 25GbE Adapter Specifications, checked 2026-10-27