3Com EtherLink/MC 4233-02 MCA Network Card IBM PS/2 Microchannel ELNK/MC Rev A

3Com EtherLink/MC 4233-02 MCA Network Card IBM PS/2 Microchannel ELNK/MC Rev A

The 3Com EtherLink/MC (model 4233-02) is a Micro Channel Architecture (MCA) Ethernet adapter designed for IBM PS/2 computers. It connects PS/2 systems to 10 Mbps Ethernet networks via BNC (10BASE2 thin coax) or AUI/DB15 (10BASE5 thick coax or external transceiver) interfaces. The board is marked "1987 3Com Made in USA 4233-02 Rev A" and carries a Sony CXK5864BM-12L controller IC as its primary network chipset.

Specifications & What's Included

• Manufacturer: 3Com Corporation
• Model / MPN: 4233-02
• Revision: Rev A
• Bus Interface: Micro Channel Architecture (MCA) — full-length card
• Network Technology: Ethernet 10BASE2 (BNC) / 10BASE5 (AUI)
• BNC connector: for 10BASE2 thin coaxial cable networks
• DB15 AUI connector: for 10BASE5 thick coax or external transceiver
• Primary controller IC: Sony CXK5864BM-12L (legible on PCB)
• Oscillator: SARONX crystal visible on PCB near controller
• Country of Manufacture: USA (printed on PCB)
• Year of manufacture: 1987
• Compatible with: IBM PS/2 systems using Micro Channel Architecture (286, 386, and later MCA-equipped PS/2 models)
• Card only — no driver diskette, software, or cables included

Applications

The EtherLink/MC was designed exclusively for IBM's PS/2 line, which introduced the proprietary Micro Channel Architecture bus in 1987 as a replacement for the ISA bus used in earlier IBM PCs. MCA offered bus mastering and improved throughput but was incompatible with ISA expansion cards, making dedicated MCA peripherals like this card necessary for PS/2 network connectivity. The 4233-02 allowed PS/2 workstations — including the Model 50, 55, 60, 70, and 80 — to join 10 Mbps Ethernet segments using either thin coax (10BASE2) or thick coax (10BASE5) cabling infrastructures common in corporate and university networks of the late 1980s and early 1990s. Today, these cards are sought by collectors restoring IBM PS/2 systems, by hobbyists running vintage OS/2 or DOS networks, and by institutions maintaining legacy MCA-based equipment. Working MCA Ethernet adapters from established network vendors like 3Com are increasingly scarce and difficult to source.