I2C = Inter IC Communication, a standard for coupling many different chips together, where a master controls many other slave chips
a do it yourself hardware project: schematics, building instructions and driver software are all published, GAL sources can be obtained freely from the author
PCF8584 bus controller
bus speed can be chosen to be 1.5, 11, 45 or 90 kHz
battery backed up clock which optionally can be used as a replacement for the motherboard RTC chips
VMC compatible expansion connector for optional modules like the Hypercom 3i