OpenSFF Management Module Specification

3. Physical Characteristics

The physical design of the Management Module (MM) ensures interoperability with all OpenSFF-compatible enclosures featuring a dedicated MM slot. All MMs, regardless of variant or capability, MUST conform to the specified dimensions, connector placement, and retention methods to guarantee interoperability across compatible enclosures.

3.1 Form Factor and Overall Dimensions

The Management Module shares the same overall length as an OpenSFF Compute Node (see Compute Node Specification, Section 3.1) to simplify backplane layout.

Accordingly, the MM MUST conform to the following overall dimensions:

The internal mechanical envelope allows the following clearances for components, heatsinks, and other structural elements:

• 22.4 mm clearance above the PCB
• 6 mm clearance below the PCB

3.2 Component Placement and Keep-Out Zones

3.2.1 Top Components

The top side of the MM PCB is typically populated with the following components:

• CPU or SoC, memory, and storage (for Full-featured MMs)
• Power delivery circuits, VRMs, passive cooling (such as heatsinks)

Maximum Dimensions for Components on the Top Side of the PCB:

• Length: 202 mm (centered): Maximum usable length, excluding the physical Management connector plug, and accounting for keep-out zones along the PCB edges facing the edge plug and the I/O shield. Exceptions are permitted for ports that exit through the I/O shield.
• Width: 102 mm (centered): Maximum usable width, allowing clearance for the air shroud (see Section 6.3) and a buffer zone for optional support structures such as PCB card guides.
• Height: 22.4 mm: Maximum top-side height, considering PCB thickness and internal shroud height (see Section 6.3).

The maximum height of 22.4 mm for top-side components SHALL be defined by the MM air shroud (see Section 6.3). For MMs with a CPU or other components exceeding a TDP of 5W, the shroud is required, and all components MUST fit entirely beneath it.

3.2.2 Bottom Components

The bottom side of the MM PCB may contain low-profile components not exceeding 6 mm

• Connectors and small ICs
• Low-profile heat spreaders
• Storage (such as M.2 NVME)

Maximum Dimensions for Components on the Bottom Side of the PCB:

• Length: 202 mm (centered): Maximum usable length, excluding the physical Management connector plug, and accounting for keep-out zones along the PCB edges facing the edge plug and the I/O shield. Exceptions are permitted only for through-hole solder tails, leads, or mechanical reinforcements associated with ports that exit through the I/O shield.
• Width: 102 mm (centered): Maximum usable width, allowing a buffer zone for optional support structures such as PCB card guides.
• Height: 6 mm: Maximum height, considering PCB thickness and clearance required for backplane mating and slot insertion.

3.2.3 General Component Placement Restrictions

Component placement on both the top and bottom of the PCB MUST be restricted in the following areas:

• Length: To accommodate keep-out zones from the I/O shield and the Enterprise connector edge plug.
• Width: To allow space for optional PCB guides and clearance for the MM’s air shroud (see Section 6.2).
• Height: To allow easy insertion and removal, and to avoid interference with the MM’s air shroud or adjacent modules.

Note: Exceptions are permitted for ports exiting through the I/O shield (top side) and for associated through-hole leads or mechanical reinforcements (bottom side).

3.3 I/O Shield

The Management Module MUST provide a metal I/O shield to function as physical protection, airflow egress, and a structural mounting surface. The I/O shield MUST also have cutouts to accommodate the external ports defined in this specification.

Required Ports:

• One RJ45 port for management networking
• Two USB Type-A ports for keyboard and mouse
• One DisplayPort output for video

The I/O shield MUST have the following dimensions:

• Width: 110 mm
• Height: 30 mm
• Thickness: 1.2 mm (minimum)

The I/O shield MUST be perforated, to act as an exhaust for the enclosure's cooling system.

The I/O shield MUST be mounted using two captive M4 thumbscrews and matching screw holes, with the following specifications:

• Mounting: Two captive M4 thumbscrews.
• Hole Center Location: 6.5 mm from top and side edges of the I/O shield.
• Screw Hole Clearance: Minimum 2.5 mm clearance around the screw hole (measured at the inside mating surface of the I/O shield).

Additional connectors on the I/O shield may be connected at the manufacturer's discretion.

3.4 Mechanical Envelope and Retention Interface

The OpenSFF management module is designed for blind-mate insertion into a compatible enclosure slot. This section defines the required mechanical envelope, rear connector alignment, and retention mechanism to ensure consistent fit and serviceability across OpenSFF enclosures.

3.4.1 Connector Alignment and Layout

The MM’s connector plug is designed for blind-mate insertion into an enclosure-defined bay envelope, which establishes the physical reference for connector positioning.

The connector MUST meet the following requirements:

• Alignment
  • The outermost guide notch shall align with the right edge of the PCB and I/O shield envelope (as viewed from the rear)
  • The connector plug MUST support blind-mate insertion without interference when following the defined bay envelope
• Layout
  • Connector position: 0mm from the left side of the PCB, including guide notch (as viewed from the connector plug side)
  • Guide notches: Provided on each side of the connector plug
  • Spacing: 34 mm between the right edge of the guide notch and the end of the PCB width (as viewed from the connector plug side)

3.4.2 Enclosure Retention Interface

The management module is secured within the enclosure using two captive M4 thumbscrews integrated into its rear I/O shield, as specified in Section 3.3. The enclosure MUST provide compatible threaded mounting points that align with the screw hole positions and support tool-less installation.

Specifically, the enclosure MUST:

• Position threaded retention points to match the MM’s 6.5 mm offset from the top and side edges of the I/O shield
• Provide a rigid backing structure to prevent flex during tightening or vibration during operation
• Maintain a 2.5 mm clearance radius around each mounting point to avoid interference with the cooling shroud
• Recess the screw mating surface by 1.2 mm from the enclosure's interior panel face to accommodate the I/O shield thickness and ensure flush contact during retention

3.5 Temperature and Humidity Requirements

The MM MUST be designed to operate within the following temperature and humidity ranges:

• Operating temperature: 10 °C to 35 °C
• Storage temperature: –40 °C to 65 °C
• Relative humidity: 8% to 80% (non-condensing)

3.6 Vibration Resistance

The MM MUST be designed to withstand vibration levels encountered in typical operating environments. See section 9.3.1 for testing specifications.

3.7 Environmental Tolerance

The Management Module MUST operate reliably in environments with typical indoor air quality, including the presence of fine dust or particulate matter (PM5 or smaller), consistent with ISO 14644-1 Class 9 cleanliness levels. The MM is NOT required to meet a formal Ingress Protection (IP) dust rating; however, they must exhibit baseline environmental resilience by withstanding standardized particulate exposure and durability validation tests. Designs SHALL NOT rely on user-replaceable air filters within the MM itself to maintain operational integrity under these conditions.

Design considerations for dust resilience:

• All components critical to system operation (including CPU sockets, memory modules, VRMs, and the like) must be positioned to limit direct accumulation of non-conductive dust
• The shroud and its airflow pathways should be designed to reduce turbulence and stagnation zones where debris can accumulate
• Where feasible, PCB coatings MAY be used to mitigate the effects of inductive or corrosive dust ingress

Serviceability Guidelines:

• The Management Module MUST be field-serviceable using non-specialized tools, with no requirement for internal cleaning during the expected lifecycle or warranty period (defined by vendor/manufacturing partner, not less than 3 years).
• Accessible areas (e.g. DIMM slots, M.2 storage slots) must remain free of obstructive debris that could impact upgrade or maintenance operations.

See section 9.2.7 for the testing requirements for dust/debris ingress.