Amiga Advanced Graphics Architecture

The Advanced Graphics Architecture chipset (AGA ) was the last generation of chipsets, which came in the Amiga computer by Commodore used. In Germany he had to be referred to as AA chipset, because the abbreviation AGA was used here already for an older PC graphics card (combination of CGA and Hercules graphics ).

He was CD ³ ² from 1992 onwards installed in the Amiga versions Amiga 1200, Amiga 4000 and Amiga and may be indicated in all screen resolutions 256 from about 16.7 million colors (24 -bit color space). In HAM8 mode, an image at all resolutions so many colors at the same time contain such pixels fit into chip RAM, minus the first column of pixels, ie at maximum chip RAM size of 2 MB up to 2 million colors. At the highest resolution, however, a maximum of approximately 830,000 pixels are simultaneously visible. These are almost real colors, but which is associated with non-negligible computational cost for optimal display. The chipset allows the display of so-called Productivity mode, that is flicker-free, high-resolution screen modes, without the aid of the OCS required for this flickerfixer, and has a maximum resolution of 1440 × 576 ( Hires interlaced overscan ).

Overall, the improvements were not sufficient to keep up with the then extended VGA - compatible graphics cards. In particular, a real, unlimited 24 -bit True Color mode was sorely missed, the mentioned 8 -bit HAM mode was not an adequate substitute. Moreover, the achievable resolutions and frame rates were no longer competitive. The memory organization bitplanes at higher color depths was complicated and slow for many applications.

Also, the AGA chipset builds indirectly on the original Original Chip Set (OCS ) on, but with some changes:

• The Agnus chip of the OCS was replaced here by Alice, she can address up to 2 MB Chip RAM.
• The Denise chip was replaced by Lisa, it provides the additional video modes.
• The Paula chip was used without change.

The successor chipset Advanced Amiga Architecture ( AAA) for AGA was already developed, but came through the bankruptcy Commodores never on the market.