How to Run ISA Network Cards with Coax Cable

Conventional networks are all about wired connections, which means there are two primary factors to consider; the type of cable and the connector. Many legacy networks were designed around the use of coaxial cable and BNC connectors.

What is ISA?

Also known as the Industry Standard Architecture, it's commonly a 16-bit bus designed to provide a common interface for computer expansion cards such as network adapters. Originally introduced in 1984 it has largely faded from use, though some specialty manufacturers still offer computers or peripherals that support it in order to maintain certain legacy hardware. There are two factors to consider when using ISA:

  • Bandwidth: 16-Bit ISA runs at between 8 and 10 MHz and offers a total bandwidth of 8 MB per second.
  • Configuration: In order to configure an ISA network adapter, you usually have to manually set the card to use the appropriate system resources using either jumpers or DIP switches.

How Do You Connect ISA Networks over Coaxial with BNC?

While both the 10Base2 and 10Base5 network standards rely on coaxial cable, neither involves a drop-in replacement for your existing TV or video cable. Networking has different requirements that don't match up with the standard 50 or 75 Ohm F-type connector used for video. The coax works, but the connectors are different. Most ISA network cards feature BNC connectors for 10Base2 Thinnet connections. BNC works around two connectors, one male and one female:

  • BNC Male: The BNC male uses a protruding center plug that fits over the female connector sleeve and mounts on one end of the cable. You simply slide it into place and then rotate the knurled outer ring a quarter turn to lock it into place.
  • BNC Female: This connector is a sleeve with two lugs on the outside. It's normally used on network cards and other fixed hardware, with the lugs enabling a positive anchor for the BNC Male.

Using 10Base2

Most BNC coaxial cable networks are 10Base2, with a maximum length of about 600 feet or just under 200 meters using a 50-Ohm BNC connector. One big advantage of this implementation is that you connect all your devices to a single cable that runs from one device to another. There is no need to cart around a hub or other similar network hardware with RG58 BNC Thinnet. Multiple computers usually connect with T-connectors which use barrel connectors to attach to the female jack on the NIC. It does suffer from lower bandwidth than later implementations, but you can still find it in legacy networks where the practical advantage of installed coaxial cable may outweigh the limitations of the system.