Advanced Graphics Architecture

The Advanced Graphics Architecture chipset ( AGA ) was the last generation of chipsets that the Amiga computer from Commodore were used. In Germany he had to as AA are called chipset, since the abbreviation AGA been here for an older PC - graphics card (combination of CGA - and Hercules graphics had been used).

It was built into the Amiga variants Amiga 1200 , Amiga 4000 and Amiga CD³² from 1992 and can display 256 out of 16.7 million colors (24-bit color space) indexed in all screen resolutions. In HAM8 mode , an image can contain as many colors in all resolutions as there are pixels in the chip RAM , minus the first pixel column, i.e. with a maximum chip RAM size of 2 MB, a maximum of 2 million colors. In the highest resolution, however, a maximum of approx. 830,000 pixels are visible at the same time. These are almost real colors , but this is associated with a not inconsiderable amount of computing effort for optimal display. The chipset enables so-called productivity modes to be displayed. H. Flicker-free, high-resolution screen modes, without the aid of a flicker fixer required for this at OCS , and has a maximum resolution of 1440 × 576 (hires interlaced, overscan).

Overall, however, the improvements were not sufficient to keep up with the expanded VGA- compatible graphics cards of the time. In particular, a real, unlimited 24-bit TrueColor mode was sorely missed, the 8-bit HAM mode mentioned was not a full replacement. In addition, the achievable resolutions and frame rates were no longer competitive. The organization of the memory via bitplanes with higher color depths was complicated and slow for many areas of application.

The AGA chipset is also indirectly based on the original original chip set (OCS), but with a few changes:

• The Agnus chip of the OCS has been replaced by Alice , she can address up to 2 MB chip RAM.
• The Denise chip has been replaced by Lisa , she provides the additional video modes.
• The Paula chip was used unchanged.

The successor chipset Advanced Amiga Architecture (AAA) for AGA had already been developed, but never came onto the market due to the Commodore bankruptcy.

See also

• Enhanced chip set
• in the article about the CD³² the explanations about the expansion chip Akiko