Microsoft InPort 900-255-018 Rev P Device Interface 8-bit ISA Mouse Card

Microsoft InPort 900-255-018 Rev P Device Interface 8-bit ISA Mouse Card

The Microsoft InPort Device Interface card is an 8-bit ISA expansion card that adds a dedicated bus mouse port to IBM PC/XT/AT and ISA-compatible desktop computers. Rather than using a serial COM port, the InPort card provides a dedicated interrupt-driven interface for Microsoft InPort bus mice, freeing up serial ports and delivering smoother, more reliable mouse input for DOS-era applications. This example is Revision P, part number 900-255-018, and was manufactured by Microsoft Corporation.

Specifications & What's Included

• Part Number: 900-255-018
• Revision: Rev P
• Manufacturer: Microsoft Corporation
• FCC ID: C3KINPORTN
• Copyright: 1986–1989
• Bus Interface: 8-bit ISA (compatible with XT Slot B and standard AT ISA slots)
• Main Controller IC: Microsoft/NCR InPort chip, marked 900110009 V1.2, NCR0381035, F844848 K9108
• Mouse Connector: 9-pin Mini-DIN (InPort bus mouse connector) on rear bracket
• Headers: PRI-INPORT (J3) and SEC-INPORT (U1/J4) onboard headers
• Interrupt Selection: Jumper block (positions 2–3–4–5) for IRQ configuration
• Slot Setting: Jumper labeled XT Slot B / Normal
• Country of Manufacture: USA
• Card only — no mouse, cables, or software included

Applications

The Microsoft InPort interface was introduced in the mid-1980s alongside Microsoft's own bus mouse line as an alternative to serial-port mice on IBM PC/XT and AT systems. Because early PCs often had only one or two serial ports — frequently occupied by modems or printers — a dedicated bus mouse card was a practical solution for adding mouse support without sacrificing a COM port. The InPort standard uses a proprietary interrupt-driven protocol distinct from the later PS/2 and serial mouse standards, and it requires either a Microsoft InPort bus mouse or a compatible third-party bus mouse wired to the InPort connector. These cards were commonly found in corporate and professional DOS workstations of the late 1980s and early 1990s running software such as Microsoft Windows 2.x/3.x, AutoCAD, and Lotus 1-2-3 with a mouse driver. Today they are sought by vintage PC enthusiasts restoring period-correct XT and AT-class systems, as well as collectors of early Microsoft hardware.