ACCESS.bus (or AB) was a twist on the existing I2C (Inter-Integrated Circuit) protocol, developed to allow connectivity between peripheral devices and computers.
It was a competitor to USB in the late 1980s and early 1990s, but wasn’t widely adopted by hardware manufacturers.
Unlike USB, AB devices plugged into each other rather than through a central hub and had a maximum speed of 100 kilobits per second, which would likely have become a bottleneck as device capabilities increased.
AB lives on in the DDC (Display Data Channel) cables that connect computers to monitors and allow them to communicate essential information.
The Tedium blog post includes links to many sources describing the AB standard and its competitors, such as SCSI, Firewire and ADB.
For more information on the history of USB, see this Hackaday article.
