‌MCIO 74 Pin X8 to 1 x U.2 NVMe SFF-8639 GEN 5 Cable length 175mm

Technical description

The MCIO 74 Pin x8 to 1 x U.2 NVMe SFF-8639 Gen 5 cable, 175 mm is a short-reach internal high-speed storage interconnect designed to connect a host-side MCIO x8 (74-pin, SFF-TA-1016) port to a single U.2 / SFF-8639 NVMe drive interface. It is intended for server, storage backplane, and workstation platforms that expose PCIe lanes through an MCIO connector and require a direct attach connection to a 2.5-inch U.2 NVMe SSD. MCIO 74-pin x8 cabling is commonly used in modern server platforms for PCIe Gen 5 class interconnects, and U.2 interfaces typically map a single NVMe drive over PCIe x4.

In a 1 x U.2 implementation, the host-side MCIO x8 connector provides more lane capacity than a single U.2 NVMe device requires. In practice, a single U.2 NVMe endpoint ordinarily uses PCIe x4, so this cable is generally deployed where the platform routes the necessary four PCIe lanes from the MCIO x8 source to one U.2 device, with remaining lane capacity either unused or platform-defined. That means the cable is physically x8 on the host side but functionally serving one U.2 NVMe drive, subject to motherboard, backplane, or HBA lane mapping. This is the key integration point to verify with the system vendor. U.2 NVMe connectivity is widely described as a 4-lane PCIe attachment.

The cable is built for PCIe Gen 5 operation, which means support for signaling up to 32 GT/s per lane on the PCIe fabric, provided the host platform, device, routing topology, and insertion-loss budget all support Gen 5 link training. As with other Gen 5 internal assemblies, cable construction typically uses controlled-impedance twinax conductors and tight pair-to-pair skew control to preserve signal integrity across high-speed differential lanes. Commercial MCIO Gen 5 cable listings commonly specify 85-ohm cable construction for these assemblies.

At 175 mm overall length, this is a very short internal cable intended for dense chassis layouts where the U.2 device bay or carrier is located close to the MCIO host connector. The short length helps reduce channel loss and supports reliable Gen 5 operation in compact server and workstation designs. Short-run MCIO assemblies are commonly used in high-density data-center and HPC hardware for exactly this reason.

Typical technical specification

Product type
Internal PCIe/NVMe storage cable assembly

Host-side connector
1 x MCIO x8, 74-pin, compliant with the SFF-TA-1016 Mini Cool Edge I/O connector family.

Device-side connector
1 x U.2 / SFF-8639 connector for a 2.5-inch NVMe SSD. Public product references often describe U.2 as SFF-8639 and usually as a PCIe x4 NVMe endpoint connection.

Protocol support
PCI Express / NVMe over internal cable assembly. MCIO product references also note broader protocol support in the connector family, but for this cable the intended application is NVMe storage.

PCIe generation
PCIe Gen 5, backward compatible in typical deployments with lower generations where supported by the host and drive. PCIe 5.0 signaling operates at 32 GT/s per lane.

Lane topology
Host interface: x8 physical
Drive interface: x4 typical for one U.2 NVMe device
Actual lane assignment depends on platform routing and firmware support.

Cable length
175 mm

Cable impedance
Typically 85 ohm differential for Gen 5 MCIO cable assemblies. This is common in vendor listings for MCIO Gen 5 cables, though the exact value should still be confirmed against the specific part drawing.

Application
Direct attachment of one U.2 NVMe SSD to a motherboard, riser, HBA, or storage controller exposing an MCIO x8 port.

Mechanical use case
Short internal cable for server nodes, storage appliances, GPU servers, and high-density workstations