Understanding the Confusing World of Bus-Connected Mice

The History of Mice Between Retrofuturism and Modern Technology

The USB port, which emerged on our computers in the 1990s, simplified the interfacing of peripherals, with the exception of a few connectors that remained somewhat challenging to use. Before the USB era, there was a variety of connectors and sockets for peripherals, often requiring their own expansion cards. Among these peripherals were mice, and Robert Smallshire provides a concise history of many incompatible standards that continue to confuse retro computing enthusiasts today.

The first widely available mice in the 1980s utilized a quadrature interface, where the output from mechanical encoders connected to the mouse ball was directly redirected to the computer interface, which contained a form of hardware decoder or microcontroller. These were gradually replaced by serial mice that used an RS-232 port, then PS/2 mice, and eventually the USB variant that you are likely using today.

Among those quadrature mice—or bus mice, as Microsoft’s marketing initially called them—there existed a frustrating variety of interfaces. Microsoft, Commodore, and Atari mice were electrically similar and shared the same 9-pin D connector, yet remained incompatible with each other. The article examines the interface cards, where we discover the familiar I/O port 8255 in action. It would have been interesting to learn about the special Sun optical mice with their unique pad, but perhaps this omission highlights the vastness of the world of bus mice.

This work has enriched our knowledge about quadrature mice, and we have used some of them in the past. If you only have a USB mouse and your computer awaits one of these rarities, do not worry; there is an adapter for that.