An OCP NIC 3.0 card connects to the server through a card-edge connector on the host board. The connector follows the SFF-TA-1002 family, and the common one is the 4C+, which has 168 pins and carries 16 PCIe lanes. This guide covers how the connector naming works, how the card sizes use it and what to check when you select one. For card dimensions and the wider OCP context, see our OCP NIC 3.0 guide.
In short:
- OCP NIC 3.0 cards mate with a card-edge connector, with the 4C+ as the common primary connector.
- Each 4C connector carries 16 PCIe lanes, so a card with a second 4C connector (the W2 width) can reach 32 lanes.
- Card sizes are SFF, TSFF and LFF. All share a 115 mm depth.
- The retention latch on the card affects serviceability as much as the connector does.
How the Connector Works
A card-edge connector is a socket on the host board that receives the gold-plated fingers on the edge of the card. There is no separate plug. The card edge is the plug, so the board thickness and edge finish are part of the connector design.
The family used here is SFF-TA-1002. One connector supplier describes its 0.60 mm pitch card-edge line as meeting SFF-TA-1002, EDSFF and OCP NIC 3.0 specifications. A card vendor lists the NIC 3.0 interface on its card as a 168-pin 4C+ connector.
4C+, 4C and 2C+
The names describe how the connector is divided:
- 4C+: two small blocks on either side of a larger block that carries the x16 data lanes. A 28-pin block at the edge, called the OCP Bay portion, carries sideband signals. Suppliers list the OCP-designated version with 168 signal pins.
- 4C: the same data block without the extra sideband block, with 140 signal pins listed in the same supplier range.
- 2C+: omits the larger data block and uses fewer pins for less PCIe connectivity.
Card Sizes and How They Use the Connector
NIC 3.0 defines three sizes, all 115 mm deep:
- SFF (small form factor): 76 mm wide, 11.5 mm thick.
- TSFF (thin small form factor): 76 mm wide, 14.2 mm thick. The extra height allows higher-power parts.
- LFF (large form factor): 139 mm wide, 11.5 mm thick.
The connector count sets the lane count. A W1 card uses a single 4C+ connector. A W2 card adds a second 4C connector for 32 PCIe lanes, which gives more board space and more bandwidth. An LFF card can use only the 4C+ connector for 16 lanes and spend the rest of the area on components.
Retention and Serviceability
The card is held in place by a latch, and the latch decides how the card is removed:
- SFF pull tab: a thumbscrew on the faceplate. The card can be serviced from outside the chassis.
- SFF ejector latch: an ejector arm locks the card in place.
- SFF internal lock: the chassis must be opened to release the card. It needs less faceplate space.
- LFF: ejector latches, in short or long versions.
Card makers say the OCP NIC 3.0 interface supports hot swap. Whether a given server supports it depends on the chassis and firmware as well as the connector, so confirm it on the server's documentation.
Selection Checklist
When you choose a host card-edge connector, ask a supplier for these:
- Compliance: does the exact part number meet SFF-TA-1002 and the OCP NIC 3.0 specification, and is it the 4C+ or 4C version you need?
- Pin count: the 168 signal pin version for the 4C+. Counts vary across a connector family, so check the part number.
- Speed rating: one supplier lists 32 GT/s to 56 GT/s for its card-edge line, with higher speeds planned. Ask for the tested speed for your whole channel, including the board.
- Mating cycles: 200 cycles is a standard rating for one supplier's line. If cards will be swapped often, ask about higher-cycle versions. One part in that range is listed at 10,000 cycles.
- Mounting style: straddle-mount, vertical, right angle and orthogonal options exist. Straddle mount sits across the board edge to save height.
- Current on power pins: one supplier states 1.1 A per power pin on its power options. Compare that with the card's power draw.
- Card edge thickness and finish: the card and the connector have to be matched.
- Cabled option: if the host board is far from the card, check whether the platform uses a cabled link. See DC-MHS and M-XIO for the cabled approach.
Frequently Asked Questions
What does 4C+ mean? It is the OCP NIC 3.0 primary connector, which has the x16 data block plus an OCP Bay sideband block. The 4C version leaves out the sideband block.
How many PCIe lanes does an OCP NIC 3.0 card have? A W1 card with one 4C+ connector has 16. A W2 card adds a 4C connector for 32.
Is OCP NIC 3.0 the same as a standard PCIe card? No. A standard add-in card uses a CEM slot. OCP NIC 3.0 uses a different card-edge connector and its own card sizes. See our CEM slot guide.
Can an OCP NIC 3.0 card use a cable instead of a direct connector? Yes. The M-XIO specification includes cabled links for NIC 3.0 cards, including the 4C+ variant.
Where to Go Next
- OCP NIC 3.0 guide: card dimensions and PCIe options.
- MCIO vs OCuLink: cabled PCIe connectors.
- OCP and ORv3 connectors hub: all OCP connector guides.
- ORv3 connector compliance checklist: what to ask a supplier.
Sources
- OCP NIC 3.0 form factors quick guide (ServeTheHome): sizes, widths, 4C+ and 2C+ layout, latch types.
- Amphenol Mini Cool Edge 0.60 mm card edge datasheet: SFF-TA-1002 and OCP NIC 3.0 compliance, pin counts, speed, mating cycles, power pin current.
- OCP NIC 3.0 card datasheet: 168-pin 4C+ interface and hot-swap statement.