Online Computer Terms Dictionary - A

Amiga

<computer> A range of home computers first released by Commodore Business Machines in early 1985 (though they did not design the original - see below). Amigas were popular for games, video processing, and multimedia. One notable feature is a hardware blitter for speeding up graphics operations on whole areas of the screen.

The Amiga was originally called the Lorraine, and was developed by a company named "Amiga" or "Amiga, Inc.", funded by some doctors to produce a killer game machine. After the US game machine market collapsed, the Amiga company sold some joysticks but no Lorraines or any other computer. They eventually floundered and looked for a buyer.

Commodore at that time bought the (mostly complete) Amiga machine, infused some money, and pushed it through the final stages of development in a hurry. Commodore released it sometime[?] in 1985.

Most components within the machine were known by nicknames. The coprocessor commonly called the "Copper" is in fact the "Video Timing Coprocessor" and is split between two chips: the instruction fetch and execute units are in the "Agnus" chip, and the pixel timing circuits are in the "Denise" chip (A for address, D for data).

"Agnus" and "Denise" were responsible for effects timed to the real-time position of the video scan, such as midscreen palette changes, sprite multiplying, and resolution changes. Different versions (in order) were: "Agnus" (could only address 512K of video RAM), "Fat Agnus" (in a PLCC package, could access 1MB of video RAM), "Super Agnus" (slightly upgraded "Fat Agnus"). "Agnus" and "Fat Agnus" came in PAL and NTSC versions, "Super Agnus" came in one version, jumper selectable for PAL or NTSC. "Agnus" was replaced by "Alice" in the A4000 and A1200, which allowed for more DMA channels and higher bus bandwidth.

"Denise" outputs binary video data (3*4 bits) to the "Vidiot". The "Vidiot" is a hybrid that combines and amplifies the 12-bit video data from "Denise" into RGB to the monitor.

Other chips were "Amber" (a "flicker fixer", used in the A3000 and Commodore display enhancer for the A2000), "Gary" (I/O, addressing, G for glue logic), "Buster" (the bus controller, which replaced "Gary" in the A2000), "Buster II" (for handling the Zorro II/III cards in the A3000, which meant that "Gary" was back again), "Ramsey" (The RAM controller), "DMAC" (The DMA controller chip for the WD33C93 SCSI adaptor used in the A3000 and on the A2091/A2092 SCSI adaptor card for the A2000; and to control the CD-ROM in the CDTV), and "Paula" (Peripheral, Audio, UART, interrupt Lines, and bus Arbiter).

There were several Amiga chipsets: the "Old Chipset" (OCS), the "Enhanced Chipset" (ECS), and AGA. OCS included "Paula", "Gary", "Denise", and "Agnus".

ECS had the same "Paula", "Gary", "Agnus" (could address 2MB of Chip RAM), "Super Denise" (upgraded to support "Agnus" so that a few new screen modes were available). With the introduction of the Amiga A600 "Gary" was replaced with "Gayle" (though the chipset was still called ECS). "Gayle" provided a number of improvments but the main one was support for the A600's PCMCIA port.

The AGA chipset had "Agnus" with twice the speed and a 24-bit palette, maximum displayable: 8 bits (256 colours), although the famous "HAM" (Hold And Modify) trick allows pictures of 256,000 colours to be displayed. AGA's "Paula" and "Gayle" were unchanged but AGA "Denise" supported AGA "Agnus"'s new screen modes. Unfortunately, even AGA "Paula" did not support High Density floppy disk drives. (The Amiga 4000, though, did support high density drives.) In order to use a high density disk drive Amiga HD floppy drives spin at half the rotational speed thus halving the data rate to "Paula".

Commodore Business Machines went bankrupt on 1994-04-29, the German company Escom AG bought the rights to the Amiga on 1995-04-21 and the Commodore Amiga became the Escom Amiga. In April 1996 Escom were reported to be making the Amiga range again but they too fell on hard times and Gateway 2000 (now called Gateway) bought the Amiga brand on 1997-05-15.

Gateway licensed the Amiga operating system to a German hardware company called Phase 5 on 1998-03-09. The following day, Phase 5 announced the introduction of a four-processor PowerPC based Amiga clone called the "pre\box". Since then, it has been announced that the new operating system will be a version of QNX.

On 1998-06-25, a company called Access Innovations Ltd announced plans to build a new Amiga chip set, the AA+, based partly on the AGA chips but with new fully 32-bit functional core and 16-bit AGA hardware register emulation for backward compatibility. The new core promised improved memory access and video display DMA.

By the end of 2000, Amiga development was under the control of a [new?] company called Amiga, Inc.. As well as continuing development of AmigaOS (version 3.9 released in December 2000), their "Digital Environment" is a virtual machine for multiple platforms conforming to the ZICO specification. As of 2000, it ran on MIPS, ARM, PPC, and x86 processors.

Home.

Amiga Web Directory.

amiCrawler.

Newsgroups: comp.binaries.amiga, comp.sources.amiga, comp.sys.amiga, comp.sys.amiga.advocacy, comp.sys.amiga.announce, comp.sys.amiga.applications, comp.sys.amiga.audio, comp.sys.amiga.datacomm, comp.sys.amiga.emulations, comp.sys.amiga.games, comp.sys.amiga.graphics, comp.sys.amiga.hardware, comp.sys.amiga.introduction, comp.sys.amiga.marketplace, comp.sys.amiga.misc, comp.sys.amiga.multimedia, comp.sys.amiga.programmer, comp.sys.amiga.reviews, comp.sys.amiga.tech, comp.sys.amiga.telecomm, comp.Unix.amiga.

See aminet, Amoeba, bomb, exec, gronk, guru meditation, Intuition, sidecar, slap on the side, Vulcan nerve pinch.

(2003-07-05)