Amiga Advanced Graphics Architecture (AGA) is the third-generation

Amiga Amiga is a family of personal computers introduced by Commodore International, Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and sign ...

graphic chipset, first used in the

Amiga 4000 The Commodore Amiga 4000, or A4000, is the successor of the A2000 and A3000 computers. There are two models: the A4000/040 released in October 1992 with a Motorola 68040 CPU, and the A4000/030 released in April 1993 with a Motorola 68EC030. ...

in 1992. Before release AGA was codenamed Pandora by

Commodore International Commodore International (other names include Commodore International Limited) was an American home computer and electronics manufacturer founded by Jack Tramiel. Commodore International (CI), along with its subsidiary Commodore Business Mac ...

. AGA was originally called AA for Advanced Architecture in the United States. The name was later changed to AGA for the European market to reflect that it largely improved the graphical subsystem, and to avoid trademark issues. AGA is able to display graphics modes with a depth of up to s per pixel. This allows for in indexed display modes and (18-bit) in

Hold-And-Modify Hold-And-Modify, usually abbreviated as HAM, is a display mode of the Commodore Amiga computer. It uses a highly unusual technique to express the color of pixels, allowing many more colors to appear on screen than would otherwise be possible ...

(HAM-8) modes. The palette for the AGA chipset has 256 entries from (24-bit), whereas previous chipsets, the

Original Chip Set The Original Chip Set (OCS) is a chipset used in the earliest Commodore Amiga computers and defined the Amiga's graphics and sound capabilities. It was succeeded by the slightly improved Enhanced Chip Set (ECS) and greatly improved Advanced G ...

(OCS) and Enhanced Chip Set (ECS), only allow out of 4096 or 64 colors in Amiga Extra Half-Brite (EHB mode). Other features added to AGA over ECS are super-hi-res smooth scrolling and 32-bit fast page memory fetches to supply the graphics data bandwidth for 8 bitplane graphics modes and wider sprites. AGA is an incremental upgrade, rather than the dramatic upgrade of the other chipset that Commodore had begun in 1988, the Amiga Advanced Architecture chipset (AAA), lacking many features that would have made it competitive with other graphic chipsets of its time. Apart from the graphics data fetches, AGA still operates on 16-bit data only, meaning that significant bandwidth is wasted during register accesses and

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...

and blitter operations. Also the lack of a chunky graphics mode is a speed impediment to graphics operations not tailored for planar modes, resulting in ghost artifacts during the common productivity task of

scrolling In computer displays, filmmaking, television production, and other kinetic displays, scrolling is sliding text, images or video across a monitor or display, vertically or horizontally. "Scrolling," as such, does not change the layout of the text ...

. In practice, the AGA HAM mode is mainly useful in paint programs, picture viewers, and for video playback. Workbench in 256 colors is much slower than ECS operation modes for normal application use; a workaround is to use multiple screens with different color depths. AGA lacks flicker free higher resolution modes, being only able to display at flicker-free operation. mode is rarely used as it can only operate at a flickering interlaced mode. In contrast, higher-end PC systems of this era can operate at with a full 256-color display. AGA's highest resolution is in interlaced when overscan is used. These missed opportunities in the AGA upgrade contributed to the

ultimately losing technical leadership in the area of

multimedia Multimedia is a form of communication that uses a combination of different content forms such as text, audio, images, animations, or video into a single interactive presentation, in contrast to tradit ...

. After the long-delayed AAA was finally suspended, AGA was to be succeeded by the Hombre chipset, but this was ultimately cancelled due to Commodore's

bankruptcy Bankruptcy is a legal process through which people or other entities who cannot repay debts to creditors may seek relief from some or all of their debts. In most jurisdictions, bankruptcy is imposed by a court order, often initiated by the debto ...

. AGA is present in the

CD32 CD32 (cluster of differentiation 32), also known as FcγRII or FCGR2, is a surface receptor glycoprotein belonging to the Ig gene superfamily. CD32 can be found on the surface of a variety of immune cells. CD32 has a low-affinity for the Fc r ...

, Amiga 1200, and

Technical details

In order to increase memory bandwidth, the Chip RAM data bus was extended to 32-bit width as in the A3000 (unlike AGA, the A3000's Chip RAM is 32-bit for CPU access only) and the Alice chip (replacing OCS/ ECS

Agnus Agnus (Latin for Domestic sheep, lamb) can be used to refer to : People with the surname * Felix Agnus (1839-1925), American military officer and newspaper publisher Religion * ''Agnus Dei'' (Latin: "Lamb of God") ** referring to Jesus Christ as d ...

) was improved to be able to support full-width access for bitplane DMA. Bandwidth was doubled again (to 4x) by using Fast Page Mode RAM. Lisa (replacing former Denise) adds support for 8-bit bitplane data fetches, 256 instances of 24-bit palette registers, and for 32-bit data transfer for bitplane graphic and sprites. The rest of the chipset remains unchanged, as do the Blitter and Copper coprocessors in Alice, still working on 16-bit data.

References

External links

mways.co.uk - How to Code the Amiga - AGA Chipset

The AGA Chip Set Functional Specification
{{Amiga hardware Amiga chipsets Graphics chips AmigaOS

Technical details

See also

References

External links