Complex sentence: In addition the A1200 features a 32-bit CPU/RAM expansion slot and a unique feature, the so-called "clock port", which is a remnant of an abandoned design feature for addition of internal RAM and a real-time clock.
Split into simpler sentences: In addition the A1200 features a 32-bit CPU/RAM expansion slot and a feature unique to the A1200, the so-called'clock port'. The clock port is a remnant of an abandoned design feature for addition of internal RAM and a real time clock.