Advanced Graphics Architecture
Encyclopedia
Advanced Graphics Architecture (AGA) is the third generation Amiga
graphic chip set, first used in the Amiga 4000
in 1992. AGA was codenamed the Pandora chipset by Commodore International
internally.
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 8 bit per pixel. This allows for 256 colors in indexed display modes and 262144 colors (18-bit) in HAM-8 (Hold-And-Modify
) modes. The palette for the AGA chipset has 256 entries from 16777216 colors (24-bit), whereas previous chip sets (OCS and ECS) only allowed 32 colors out of 4096. Other features added to AGA over ECS were super hires smooth scrolling and 32-bit fast page memory fetches to supply the graphics data bandwidth for 8 bitplane graphics modes and wider sprites.
AGA was an incremental upgrade, rather than the dramatic upgrade of the other chipset that Commodore had begun in 1988, AAA
, lacking many features that would have made it competitive with other graphic chip sets of its time. Apart from the graphics data fetches, AGA still operated on 16-bit data only, meaning that a lot of bandwidth was wasted during register accesses and copper and blitter
operations. Also the lack of a chunky graphics mode was a speed impediment to graphics operations not tailored for planar modes. In practice, the AGA HAM (Hold-And-Modify
) mode was too slow to be useful except for displaying static images. Also, Workbench in 256 color AGA was of concern, being much slower than ECS operation modes for normal application use. AGA also lacked flicker free higher resolution modes; being only able to display 640x480 at 72Hz flicker-free operation. 800x600 mode was rarely used as it could only operate at a flickering 60Hz interlaced mode. In contrast, higher-end PC systems of this era could operate 1024x768 at 72Hz with a full 256 color display (AGA highest resolution 1280x512).
These missed opportunities in the AGA upgrade may have contributed to the Amiga
ultimately losing technical leadership in the multimedia
area. AGA was to be succeeded by the Hombre chipset
, after the long delayed AAA was finally shelved, which was ultimately cancelled due to Commodore's bankruptcy
.
AGA was used in the CD32
, Amiga 1200
and Amiga 4000
.
data bus was extended to 32 bit width (as in the A3000
) and the Alice chip (replacing OCS/ECS Agnus) was improved to be able to support full width access. Additionally, the memory clock was doubled.
Lisa (replacing former Denise) added support for 8 bit bitplane data fetches, 256 24-bit palette registers, and for 32 bit data transfer for bitplane graphic and sprites.
The rest of the chipset remained unchanged, as did the Blitter and Copper coprocessors in Alice, still working on 16-bit data.
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
graphic chip set, first used in the Amiga 4000
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. AGA was codenamed the Pandora chipset by Commodore International
Commodore International
Commodore is the commonly used name for Commodore Business Machines , the U.S.-based home computer manufacturer and electronics manufacturer headquartered in West Chester, Pennsylvania, which also housed Commodore's corporate parent company, Commodore International Limited...
internally.
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 8 bit per pixel. This allows for 256 colors in indexed display modes and 262144 colors (18-bit) in HAM-8 (Hold-And-Modify
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....
) modes. The palette for the AGA chipset has 256 entries from 16777216 colors (24-bit), whereas previous chip sets (OCS and ECS) only allowed 32 colors out of 4096. Other features added to AGA over ECS were super hires smooth scrolling and 32-bit fast page memory fetches to supply the graphics data bandwidth for 8 bitplane graphics modes and wider sprites.
AGA was an incremental upgrade, rather than the dramatic upgrade of the other chipset that Commodore had begun in 1988, AAA
AAA chipset
The AAA chipset was intended to be the next-generation Amiga multimedia system designed by Commodore International. Initially began as a secret project, the first design discussions were started in 1988, and after many revisions and redesigns the first silicon versions were fabricated in 1992-1993...
, lacking many features that would have made it competitive with other graphic chip sets of its time. Apart from the graphics data fetches, AGA still operated on 16-bit data only, meaning that a lot of bandwidth was wasted during register accesses and copper and blitter
Blitter
In a computer system, a blitter is a circuit, sometimes as a coprocessor or a logic block on a microprocessor, that is dedicated to the rapid movement and modification of data within that computer's memory...
operations. Also the lack of a chunky graphics mode was a speed impediment to graphics operations not tailored for planar modes. In practice, the AGA HAM (Hold-And-Modify
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....
) mode was too slow to be useful except for displaying static images. Also, Workbench in 256 color AGA was of concern, being much slower than ECS operation modes for normal application use. AGA also lacked flicker free higher resolution modes; being only able to display 640x480 at 72Hz flicker-free operation. 800x600 mode was rarely used as it could only operate at a flickering 60Hz interlaced mode. In contrast, higher-end PC systems of this era could operate 1024x768 at 72Hz with a full 256 color display (AGA highest resolution 1280x512).
These missed opportunities in the AGA upgrade may have contributed to the Amiga
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
ultimately losing technical leadership in the multimedia
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...
area. AGA was to be succeeded by the Hombre chipset
Hombre chipset
The Hombre chipset was to be a chipset for use in game machine hardware. However, because of Commodore International's bankruptcy, the Hombre chipset was never released.-History:...
, after the long delayed AAA was finally shelved, which was ultimately cancelled due to Commodore's bankruptcy
Bankruptcy
Bankruptcy is a legal status of an insolvent person or an organisation, that is, one that cannot repay the debts owed to creditors. In most jurisdictions bankruptcy is imposed by a court order, often initiated by the debtor....
.
AGA was used in the CD32
Amiga CD32
The Amiga CD32, styled "CD32" , was the first 32-bit CD-ROM based video game console released in western Europe, Australia, Canada and Brazil. It was first announced at the Science Museum in London, United Kingdom on 16 July 1993, and was released in September of the same year...
, Amiga 1200
Amiga 1200
The Amiga 1200, or A1200 , was Commodore International's third-generation Amiga computer, aimed at the home market...
and Amiga 4000
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....
.
Technical detail
In order to increase memory bandwidth, the Chip RAMChip RAM
Chip RAM is a commonly used term for the integrated RAM used in Commodore's line of Amiga computers. Chip RAM is shared between the central processing unit and the Amiga's dedicated chipset...
data bus was extended to 32 bit width (as in the A3000
Amiga 3000
The Commodore Amiga 3000, or A3000, was the third major release in the Amiga computer family. Released in June 1990, it features improved processing speed, improved rendering of graphics, and a new revision of the operating system...
) and the Alice chip (replacing OCS/ECS Agnus) was improved to be able to support full width access. Additionally, the memory clock was doubled.
Lisa (replacing former Denise) added support for 8 bit bitplane data fetches, 256 24-bit palette registers, and for 32 bit data transfer for bitplane graphic and sprites.
The rest of the chipset remained unchanged, as did the Blitter and Copper coprocessors in Alice, still working on 16-bit data.
See also
- AAAAAA chipsetThe AAA chipset was intended to be the next-generation Amiga multimedia system designed by Commodore International. Initially began as a secret project, the first design discussions were started in 1988, and after many revisions and redesigns the first silicon versions were fabricated in 1992-1993...
- Amiga Ranger ChipsetAmiga Ranger ChipsetAmiga Ranger was a prototype computer that was supposed to be the second generation Amiga chipset prior to ECS. It was designed by the original Los Gatos Amiga team including Jay Miner. However Commodore International didn't release this chipset due to its high cost-History:After the release of...
- ECSEnhanced Chip SetThe Enhanced Chip Set is the second generation of the Amiga computer's chipset, offering minor improvements over the original chipset design. ECS was introduced in 1990 with the launch of the Amiga 3000. Amigas produced from 1990 onwards featured a mix of OCS and ECS chips, such as later versions...
- AA+Commodore AA+ ChipsetThis was the last classic Amiga compatible chipset that Commodore announced in 1992. They planned to release it in 1994 for low end Amiga computers along with AAA.-History:...
- Hombre chipsetHombre chipsetThe Hombre chipset was to be a chipset for use in game machine hardware. However, because of Commodore International's bankruptcy, the Hombre chipset was never released.-History:...
- List of home computers by video hardware
- OCSOriginal Amiga chipsetThe Original Chip Set was a chipset used in the earliest Commodore Amiga computers and defined the Amiga's graphics and sound capabilities...