OpenSFF Compute Node Specification

5. Connector Specifications

5.1 4C+ Connector (Core)

General Description: The 4C+ connector, referred to in this specification as the Core connector, is a card edge interface based on the SFF-TA-1002 specification. It is used in both Core and Enterprise compute nodes, and features 168 contacts and supports up to 52 differential pairs of high-speed signals.

5.1.1 Pin Assignment

The 4C+ connector used in OpenSFF compute nodes follows a standardized pin configuration optimized for signal integrity, interoperability, and power distribution. The layout includes:

• Predefined ground pins distributed throughout the connector to minimize impedance and improve return path quality
• Dedicated power and management pins, which MUST NOT be reassigned for signaling purposes
• High-speed signal lanes arranged in a GSSGSSG pattern to support clean differential pair routing and minimize crosstalk

Both Core and Enterprise variants of the OpenSFF compute node MUST use the 4C+ pinouts as specified in Figure 5.1.1.

Note: Reserved pins MAY be used by manufacturers to add features to the compute node, such as additional I/O ports.

5.1.2 Supported Protocols

The 4C+ connector is designed for multi-protocol operation and supports simultaneous use of:

• PCIe Gen 3 / 4 / 5 / 6
• Ethernet
• USB 2.0 / USB 3.x / USB4
• DisplayPort 1.4 or newer
• I2C / SMBus / Sideband signals
• NVMe, SATA, SAS (depending on system design)

5.1.3 Electrical Characteristics

Key electrical parameters of the 4C+ connector are as follows:

• Signaling Rate: Up to 112 GT/s PAM4
• Impedance: This specification does not restrict, require or define a specific impedance for the connector.
• Voltage / Current Ratings:
  • Max voltage: 12 VDC
  • Max current: 1.1 A per power contact, 0.5 A per signal contact
  • Temperature rating: –40 °C to 85 °C
• Power Integrity:
  • The connector includes an internally linked ground network that provides a low-inductance, low-impedance return path for high-speed signals.

5.1.4 Mechanical Characteristics

• Mating Style: Card edge
• Mating Cycles:
  • ≥ 200 (Grade 2 durability)
  • Connector wipe length: 0.40 mm (Gold-Gold interface)
• Mounting Type: Surface Mount Technology (SMT)
• Dimensions (Straddle Mount):
  • Width: 73 mm
  • Pitch: 0.60 mm
  • Height: 10.05 mm max
  • Compatible with host PCB thickness of 1.57±0.13 mm

5.2 4C Connector (Enterprise)

General Description: The 4C connector, referred to in this specification as the Enterprise connector, is used exclusively in Enterprise variant compute nodes. It is a card edge interface based on the SFF-TA-1002 specification. It features 140 contacts and supports up to 44 differential pairs of high-speed signals.

5.2.1 Pin Assignment

The 4C connector used in OpenSFF compute nodes follows a standardized pin configuration optimized for signal integrity and interoperability. The layout includes:

• High-speed signal lanes arranged in a GSSGSSG pattern to support clean differential pair routing and minimize crosstalk
• Predefined ground pins distributed throughout the connector to minimize impedance and improve return path quality

Enterprise variants of the OpenSFF compute node MUST use the 4C pinouts as specified in Figure 5.2.1.

5.2.2 Supported Protocols

The 4C connector supports a variety of signaling protocols and sideband interfaces, including:

• PCIe Gen 3 / 4 / 5 / 6
• Ethernet
• USB 2.0 / USB 3.x / USB4
• DisplayPort 1.4 or newer
• I2C / SMBus / Sideband signals
• NVMe, SATA, SAS (depending on system design)

5.2.3 Electrical Characteristics

Key electrical parameters of the 4C+ connector are as follows:

• Signaling Rate: Up to 112 GT/s PAM4
• Impedance: This specification does not restrict, require or define a specific impedance for the connector.
• Voltage / Current Ratings:
  • Max voltage: 12 VDC
  • Max current: 1.1 A per power contact, 0.5 A per signal contact
  • Temperature rating: –40 °C to 85 °C
• Power Integrity:
  • The connector includes an internally linked ground network that provides a low-inductance, low-impedance return path for high-speed signals.

5.2.4 Mechanical Characteristics

• Mating Style: Card edge
• Mating Cycles:
  • ≥ 200 (Grade 2 durability)
  • Connector wipe length: 0.40 mm (Gold-Gold interface)
• Mounting Type: Surface Mount Technology (SMT)
• Dimensions (Straddle Mount):
  • Width: 60.8 mm
  • Pitch: 0.60 mm
  • Height: 10.05 mm max
  • Compatible with host PCB thickness of 1.57±0.13 mm