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The Amiga's Custom Chips - ICS

The Inital Chip Set was generally referred to as the PAD, taking its name from the inital letters of the three custom chips, Portia, Agnus and Daphne. It is often ambiguously called the Original Chip Set which actually refers to a different set of chips. The Inital Chip Set was the first Custom Chip Set used in the Amiga and was only used in the A1000 and what was known as the original A2000 produced in Germany which was based on the A1000.

Portia The custom chip responsible for all of the generated sounds. The sound generated by the Portia chip was unique in the computer world at the time it was released, and to a large extent charged the way people viewed computer sound. Up until this time the only sound was a series of beeps or modulated sound using a piezo crystal which sounded like a very sick telephone.
Agnus The custom chip used to control and move data to be displayed on the screen. It was also responsible for timing the machine and even directed animation. Agnus has since been upgraded a number of times, but the initial chip designation was "8361" which utilised 512 Kilobytes of CHIP RAM, to provide 5 bit colour.
Daphne The custom chip responsible for the video output and for maintaining the screen display. The output did not conform to any of the standards being developed at the time, and since most computers sold were still monochrome, the full-colour images, albeit restricted to a limited number of colours, was still impressive.


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Revised: September 25, 2005.