Advanced Graphics Architecture
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de:Advanced Graphics Architecture pl:AGA
Advanced Graphics Architecture (AGA) was the name used for the improved graphics chipset of the third generation Amiga computers at the beginning of the 1990s. Second generation had ECS.
AGA is able to do 8-bit (256 colors) in normal display mode and 262144 colors in Hold and Modify (HAM) mode (18-bit color, 6-bit per RGB channel). Palette for AGA chipset is 16777216 colors (24-bit). The original Amiga chipset (OCS) had 4096 colors (12-bit, 4-bit per RGB channel), of which 32 could be displayed unless in half-bright (which provided an additional 32 colors fixed at half the brightness of the first 32) or HAM mode. Other features added to AGA over ECS were superhires smooth scrolling and 32-bit memory fetches to supply the graphics data bandwidth for 8 bitplane graphics modes.
Unfortunately many opportunities to add further improvements, which would have made the chipset more competitive, were missed. Apart from the graphics data fetches the chipset still operates on 16-bit data only, meaning that a lot of bandwidth is wasted during register accesses and copper and blitter operations. Also no chunky graphics mode was added, which puts the AGA amigas in great disadvantage in CPU intensive graphics operations. Over all the AGA chipset was a quick design fix and not the (then) necessary redesign of the Amiga, adding further to Commodores technical decline.
AGA was included in the CD32, Amiga 1200 and Amiga 4000.