Sounds like the Rev. A iMacs where you could add a floppy drive and an ADB port just by adding the connectors. There was already a serial port - just disconnect the rarely-used internal infrared receiver, and connect your serial device to the port that says "NOT A SERIAL PORT".

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Neat trick. Plus, you can actually regain IR via a USB device. I've heard of a couple that work with the iMac if you want to turn it into a set top media player.

Incidently, Apple didn't completely discontinue ADB until about 2004 (not 1999). Certain Macbooks used it as an internal bus between the trackpad and keyboard.

And legend has it that Woz developed it one month because he was bored.

- John