Genuine Sun Microsystems SBUS I/O expansion board, field‑replaceable unit 501‑4883‑03, built on PCB 270‑4266‑04 REV 50. This board served as a system‑level I/O interface in mid‑1990s Sun SPARCserver and SPARCstation chassis, providing internal routing and support for SBUS daughtercards (not included).

• Condition: Complete overall, with one noted defect.

• Status: Untested — I do not have the chassis required to verify functionality.

• Connector note: The rightmost SBUS card‑edge socket has a visible dent approximately 1 cm from the left end. The plastic housing is deformed in that area; see photos for detail.

• Chips: Includes original Sun ASICs (STP20020FP and 100‑4262‑02).

• Form factor: Eurocard‑style vertical mount with DIN connectors.

• Use case: Suitable for restoration projects, parts harvesting, or repair by someone equipped to replace the SBUS Matches systems requiring FRU 501‑4883‑03; please confirm with your chassis documentation.

Ships safely packed in antistatic and foam material.

This FRU is one of the less common I/O backplane modules from the mid‑90s Sun workstation/server era. Boards like this often go missing when systems are parted out, making them valuable for anyone restoring a chassis to period‑correct configuration. The original Sun ASICs and intact FRU labeling make it a solid candidate for collectors who appreciate completeness and authenticity, with the connector damage reflected in the price.BONUS clear plastic heatsink airflow deflector shield, P/N 330-2304-01,