Misplaced Pages

This is an old revision of this page, as edited by Gatoclass (talk | contribs) at 01:43, 1 May 2006 (→Operating systems: Modest rewrite of AmigaOS section for greater clarity. Also added some info about OS and AGA.). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

This article is about the family of home computers. For other uses, see Amiga (disambiguation).

The Amiga is a family of home/personal computers originally developed by Amiga Corporation as an advanced game console. Development on the Amiga began in 1982 with Jay Miner as the principal hardware designer. Commodore International introduced the machine to the market in 1985, after having bought Amiga Corp. The machine was ahead of its time, sporting a custom chipset with advanced graphics and sound capabilities, and a sophisticated multitasking operating system, now known as AmigaOS. Based on the Motorola 68k series of 32-bit microprocessors, the Amiga provided a significant upgrade from 8-bit computers such as the Commodore 64, and the Amiga quickly grew in popularity among computer enthusiasts, especially in Europe. It also found a prominent role in the video production business.

History

The Amiga was originally designed by a small company called Amiga Corporation as the ultimate video games machine. Before the machine was released into the market, the company was bought out by Commodore, and it was redesigned into a real, general-purpose computer. The first model, called the Amiga 1000, was released in 1985 as a successor to the Commodore 64 and a rival to the Atari ST.

For more information, see Did Atari attempt to acquire Amiga?

Commodore later released several new Amiga models, both for low-end gaming use and high-end productivity use. Throughout the 1980s, the Amiga's combination of advanced hardware and operating system software offered greater power than its competitors, but in the 1990s, other platforms, most of all the PC, reduced or eliminated this advantage.

Hardware

At the time of its introduction in 1985, the Amiga was the most advanced computer ever designed for the home market. It offered a fast CPU, enormous memory expansion capability (while IBM and other PC-clones were running into the 640K memory limit built into their design), powerful sound and graphics subsystems, and one of the first multitasking operating systems for personal computers. It was popular in the home, and, to a lesser extent, in business environments, where it was used largely for its video editing capabilities.

CPU

The very first model, the Amiga 1000, had a 7.16 MHz 68000 CPU (7.09 MHz for PAL machines). The CPU clock frequency is precisely double the 3.58 MHz NTSC color carrier frequency (and double the corresponding PAL color carrier frequency), which eased working directly with NTSC video.

Later models came with 68020, 68030, 68040 and 68060 CPUs. These CPUs as well as the 68010 were available as upgrades. PPC upgrades were also available as co-processors (albeit very little software was written to take advantage of the PowerPC).

Custom chipset

The Original Amiga chipset, or OCS, is more advanced than other architectures of its time: it has dedicated chips for real-time video effects, allowing users to work with genlocks to overlay graphics atop live video. The Amiga's overscan feature allows it to draw images past the visible borders of a television screen, allowing seamless fly-ins and scrolling from off-frame.

The machine is expandable and supports what was considered a large amount of memory at that time. The original machine shipped with 256K and offered an initial expansion to 512K. That first 512K of memory is Chip RAM, which means it's shared between the custom chipset and the CPU, with the chipset having priority. Additional RAM, up to 8 more megabytes, can be attached via the side expansion bus, and was visible only to the CPU. A mere 8 megabytes may seem laughably small to a modern reader, but at the time, that much RAM would have cost around $300 US. Memory efficiency was one of the strong points (and still is!) of the Amiga OS.

The Amiga has no text mode, offering only bitmapped graphics. It uses 'planar' graphics, meaning that display memory buffers are arranged in bitplanes. A 1-bitplane image provided 2 colors (usually black and white): this would be the equivalent of the early Macintosh display. Each additional bitplane doubles the number of available colors. Low-resolution modes support up to 5 planes (and, thus, 32 colors), while high-resolution modes support 4 (16 colors). Each color can be chosen from the system palette of 4,096. This planar arrangement is a bit tricky to manipulate with the CPU, because any given pixel on the screen can be represented by up to 5 disparate bytes in memory. The blitter handled most of this automatically.

To get around some of the color limitations, the Amiga also offers a unique HAM (Hold And Modify) graphics mode. In this low-resolution mode, a pixel can be any of the 16 basic colors, exactly like regular low-res screens. In addition, a given pixel can H)old the value from the previous pixel, and M)odify either the red, green, or blue value, which expanded the number of colors displayed to 4096. Once software was developed that could encode images this way, a striking set of amazingly realistic still pictures began circulating. This mode is hard to program, and in the early days was mostly used only for slideshows and video overlays.

The video chipset is configurable, supporting programmable resolutions and the ability to double the vertical resolution of the screen by switching to interlaced mode. This is intended for use with televisions, as their signals are also interlaced. This allowed the Amiga to be the first useful personal computer for video applications.

Programmable resolutions makes it possible for the Amiga to shift quickly between NTSC and PAL resolutions; the exact same hardware was sold in both areas. By specifying large overscan values, it can go past the borders of nearly all televisions. This allows it to 'fly-in' objects from off-frame, and was absolutely crucial to its success in the video market.

Due to flicker, many are unwilling to use the higher-resolution display offered by interlace. This led to a small market for flicker fixers. Early "fixers" were just a piece of smoked glass velcroed onto the monitor; decreasing the contrast reduced the apparent flicker. Later, there were hardware deinterlacers, and eventually Commodore shipped versions of the Amiga that could produce the higher resolutions natively.

The CPU needs access to Chip RAM only during the even cycles. The odd cycles were used exclusively by the chipset. The blitter, though, had a flag that, if enabled, would allow it to access Chip RAM during the even cycles, blocking the CPU. Sometimes, enabling it made a lot of sense since the blitter could do its job a whole lot faster than the CPU could emulate it, enabling the Amiga to do some kind of jobs in realtime that it could not do otherwise, or just to do them in a shorter amount of time. The copper holds an even higher priority accessing Chip RAM, because of its realtime nature. When the chipset blocks access to Chip RAM to the CPU, the CPU can still access the so-called Fast RAM, which chipset cannot access.

The Amiga's architecture, however, has a drawback in high-resolution modes. With the chipset sharing memory bandwidth with the CPU, overall system performance decreased with increasing resolutions and color depth. At 16 colors, for instance, it slows CPU access enough to cut the machine's speed roughly in half. Because of this, high-resolution 16-color screens were mostly avoided until later in the Amiga's evolution, when RAM (FASTMEM) expansion became routine.

Later Amiga models include improved versions of the chipset: The Enhanced Chip Set (ECS) and the Advanced Graphics Architecture (AGA).

Video applications

Today, many TV stations and broadcast corporations are still using A3000s and A4000s for their real-time video effects. Many programs have also been written for creating "fansubs" of foreign films and Japanese animation. Many competing products have been created for the Amiga's video capabilities ranging from simple genlocks that allows you to simply switch the RGB overlay feed on and off, to more advanced devices like the Supergen which has faders, and the ultimate expression of the Amiga's native power, the Newtek Video Toaster. Other interesting products that use the genlock capability enable users to do motion tracking and interactivity, 20 years before similar products like the Sony EyeToy for the PlayStation 2 video-game console.

Genlock

Due to its ability to genlock, that is, adjust its own screen refresh timing to match the signal from a VCR, the Amiga also has a niche market among biologists analyzing video recordings of organisms in motion at a time when other systems capable of doing similar tasks cost an order of magnitude more. At the time, several video boards for IBM-compatible systems could overlay computer-generated graphics on top of the signal from a video camera, but these boards require the camera to accept a sync pulse from the computer, so they are useless for overlaying graphics on VCR output. In the late 1980s the Amiga was for some biologists working on limited budgets the only affordable way to do kinematic analysis of video captured by a VCR.

Sampling

The Amiga was one of the first computers for which one could buy cheap accessories for sound sampling and video digitization. This means that not only can the Amiga produce computer-generated images and sound, but users can input "real" images and sound for editing, composition, and use in computer games.

Sound

The original sound chip supports four real-time sound channels (2 of them earmarked for the left speaker and 2 for the right) with 8 bits' resolution for each channel. Further, there is a 6 bit volume on each channel, giving a total of 16 bits of data shared across the channels, volume levels and sound resolution. Software such as Octamed use software mixing to allow 8 or more virtual channels, and astute composers can mix two hardware channels to achieve 9 bits' resolution, or all four to achieve 10 bits' resolution, which approaches the limitations of human hearing. Later, programmers developed a 14 bit stereo output routine by combining channels and volume controls with the existing 8 bit sound resolution. In the PC/Amiga rivalry, the quality of the Amiga's sound output, and the fact that the hardware is ubiquitous and easily addressed by software, was the standout feature of Amiga hardware that the PC lagged behind for years.

Several third party sound cards started to appear providing DSP functions, multitrack direct to disk recording, multiple hardware sound chanels and 16 bit and beyond resolutions. Later a retargetable sound API called AHI was developed allowing these cards to be used transparently by the OS and software.

Third party hardware

Many expansion boards are produced for Amigas to improve the performance and capability of the hardware, such as memory expansions, SCSI controllers, CPU boards, graphics boards; famous hardware manufacturers are Great Valley Products (GVP) and Phase5. Later small manufacturers include Individual Computers. Other upgrades included genlocks, ethernet cards, modems, sound cards and samplers, video digitisers, USB cards, extra serial ports, and IDE controllers.

The most popular upgrades are memory, SCSI controllers and CPU accelerator cards. These are sometimes combined into the one device, particularly on big box Amigas like the A2000, A3000 and A4000.

Early CPU accelerator cards feature full 32bit CPUs of the 68000 family such as the 68020 and 68030, almost always with 32bit memory and usually with FPUs and MMUs or the facility to add them. Later designs feature the 68040 and 68060. Both CPUs feature integrated FPUs and MMUs. Many CPU accelerator cards also feature integrated SCSI controllers. Phase5 designed the PowerUp boards (BlizzardPPC and CyberstormPPC) featuring both a 68k (a 68040 or 68060) and a PPC (603 or 604) CPU, which were able to run the two CPUs at the same time (and shared the system memory). The PPC CPU on PowerUp boards are usually used as a coprocessor for heavy computations (a powerful CPU is needed to run for example MAME, but even decoding JPEG pictures and MP3 audio was considered heavy computation in those years). It is also possible to ignore the 68k CPU and run Linux on the PPC (project Linux APUS), but a PPC native Amiga OS was not available when the PPC boards appeared.

There are also available 24 bit graphics cards and video cards. Graphics cards are designed primarily for 2D artwork production, workstation use, and later, gaming. Video cards are designed for inputing and outputting video signals, and processing and manipulating video.

Perhaps the most famous video card in the North American market is the Newtek Video Toaster. This is a powerful video effects board which turns the Amiga into an affordable video processing computer which found its way into many professional video environments. Due to its NTSC only design it did not find a market in countries that used the PAL standard, such as in Europe. In PAL countries the Opalvision card is popular, although less featured and supported than the Video Toaster.

Various manufacturers started producing PCI busboards for the A1200 and A4000, allowing standard Amigas to use PCI cards such as Voodoo graphic cards, Soundblaster sound cards, 10/100 ethernet and TV tuners.

PowerPC upgrades with Wide SCSI controllers, and PCI busboards with ethernet, sound and graphics cards, and towerised cases allowed the A1200 and A4000 to survive well into the late nineties as modern and competitive machines.

Models and variants

Classic Amiga models, from the 1000 to the 4000, were produced from 1985 to 1996. Since then, no new generations have been produced. In addition, some companies released unofficial Amiga clones. AmigaOS 4 and beyond will run on both Amigas equipped with CyberstormPPC or BlizzardPPC accelerator boards, and on third party hardware such as the PPC based Teron series motherboards when sold under the licensed AmigaOne trademark.

Amiga emulators

Some modern-day "Amiga users" actually emulate the machine on modern hardware rather than running their software on the original hardware.

Operating systems

AmigaOS

At the time of release AmigaOS was the only consumer oriented operating system to feature both true multitasking and a GUI. This, coupled with closely integrated custom hardware, gave the average consumer the experience of an OS well ahead of its time.

The OS was not without its flaws, however, the most important being lack of memory protection. While the decision to omit this feature increased performance, it also made the machine more vulnerable to crashes from badly written programs than it otherwise might have been.

The problem was somewhat exacerbated by Commodore's initial decision to release documentation relating not only to the OS's underlying software routines, but also to the hardware itself, enabling intrepid programmers to "poke" the hardware directly. While the decision to release this documentation was a popular one, it also contributed to system instability as some programmers lacked the expertise to program at this level. For this reason, when the new AGA chipset was released, Commodore declined to release documentation for it, forcing most programmers to adopt the approved software routines.

Whether the above flaw actually made Amigas less reliable than other home PC's of the period is perhaps a matter of opinion. With properly written software, it was always very stable. The OS has, however, become more stable, and more hardware independent, with each new OS release. AmigaOS is still very usable today.

*NIX

Commodore-Amiga produced Amiga Unix, informally known as Amix, based on AT&T SVR4. It supported the A2500 and A3000 and was included with the A3000UX. There are still enthusiasts running Amix but it was never supported on the later Amiga systems based on 68040 or 68060.

Other, still maintained, operating systems are available for the classic Amiga platform, including Linux and NetBSD. Both require a CPU with MMU such as the 68020 with 68551 or full versions of the 68030, 68040 or 68060. There is a version of Linux for PPC accelerator cards. Debian and Yellow Dog Linux have been made to run on the AmigaOne.

There is an official, older version of OpenBSD. The last Amiga release is 3.2.

The bootblock

The very first production Amiga, the Amiga 1000, needs to load Kickstart from floppy disk into 256 kilobytes of RAM reserved for this purpose. Some games (notably Dragon's Lair) provide an alternative codebase to install, in order to use the extra 256 kilobytes of RAM for game material.

However, subsequent Amigas hold Kickstart in a ROM chip. When the machine is started, Kickstart displays a hand holding a disk, inviting the user to insert the Workbench disk (or some other disk). The first two sectors of the disk (512 bytes) are loaded into RAM and control is passed to it.

Most entertainment software, especially during the Kickstart 1.* years, contains a bootblock that loads the rest of the software from the disk and then pass control to it. The game or demo then summarily take control of memory and resources to suit itself, effectively disabling AmigaOS. The GUI can never be invoked. Therefore, most games and demos do not use the operating system at all. Alternatively, it can be said that they install their own custom operating system since any such program must install custom interrupt handlers and so on in order to be of any use.

A floppy disk bootblock may alternatively contain code to load the dos.library (AmigaDOS) and then exit to it, invoking the GUI. Any such disk, no matter what the other contents of the disk, is known as a "DOS disk".

The bootblock became an obvious target for virus writers. Custom bootblock loaders started to be created, which check for the presence of rutines pointed by the reboot vectors or hooks in libraries before loading the dos.library, in order to detect viruses. If one installs a DOS bootblock (or a virus surruptitiously installs itself) over those custom bootblocks which don't continue the boot process as normal (such as those present in many games), it will ruin the software.

Emulation

The Amiga is able to emulate other computer platforms which were in its same price range, most notably the IBM PC and the Apple Macintosh. There are also emulators available for many 8 bit systems such as the Commodore 64, Apple II and even the TRS-80. MAME (the arcade machine emulator) is also available for Amigas with PPC accelerator card upgrades.

Amiga software

The Amiga was a primary target for productivity and game development during the late 1980s and early 1990s. Software was often developed for the Amiga and the Atari ST simultaneously, since the ST shared a similar architecture.

Amiga community

The Amiga is considered by some to have an extraordinarily loyal fan base. When Commodore went bankrupt in 1994, there was still a very active Amiga community, and this continued to support the platform long after mainstream commercial vendors abandoned the platform. The most popular Amiga magazine, Amiga Format, continued to publish editions until 2000, some six years after the last new Amiga was sold. To this day, there are still many fans who believe that the Amiga is unique and was better than other platforms.

One reason for this loyalty is due to the strengths of the machine at the time: it has a stable, compact, efficient, multitasking OS, it is relatively easy to program for, software has relatively easy access to the hardware (the base hardware was fixed so software could be coded specifically to the hardware), there is a wealth of quality software, and it was an affordable multimedia machine for its time.

However as time wore on, the hardware was overtaken and as the PC improved in software and hardware the Amiga started to look dated. Despite this, its solid userbase continues to produce software and get as much as they possibly can out of the machine. Amiga users manage to squeeze every drop of performance and capability out of the machines, with software and hardware expansions to enhance its capabilities. Even today (mid 2006) there is enough demand for expansion hardware to keep some small scale manufacturers in business.

After Commodore went bankrupt

The bankruptcy of Commodore in 1994 severely stunted the Amiga's growth. Production was halted briefly, until it was restarted for a short time under Escom's Amiga Technologies. Though the machines had been upgraded and had plentiful hardware and software support, the lack of new Amigas meant that vendors simply moved on. Most of the 'leading edge' technology hobbyists and productivity market moved to PC architecture.

Due to the fierce loyalty of some Amiga fans, the 'scene' continue, many years even after the last original Amiga was sold. Inevitably, though, the PC sooner or later became the undisputed leading home computing technology, and the console wars also left the CD32 for dead.

The rights to the Amiga platform were later successively sold to Escom and later Gateway 2000, but neither of them managed to do much with them. Finally, an entirely new company called Amiga, Inc. (no relation to the original Amiga Corporation) was founded to manage the Amiga product line. Even though Amiga, Inc. has paid considerably more attention to the Amiga product line than Escom or Gateway 2000, because of the extremely small demand in the mainstream market, development has been slow and sales have been poor.

In 2002, Eyetech in cooperation with Amiga Inc, began selling a limited number of AmigaOnes. The "AmigaOne SE" was Mai Logic's Teron CX motherboard from 2001 based on the POP (PowerPC Open Platform) design, and development to adapt AmigaOS 4 to this hardware began. The AmigaOne SE was succeeded by the Teron PX, a newer design with a replacable CPU module which came in G3 and G4 flavours. The Teron PX was marketed by Eyetech as the AmigaOne XE. In 2004, Eyetech began selling the Teron Mini as the Micro-A1, a mini-ITX model with a 750GX G3 CPU was released. The older Amigas are sometimes referred to as "Classic Amigas" to avoid possible confusion with AmigaOnes or other third party hardware bearing Amiga-like trademarks.

AmigaOnes are not currently being produced or sold. It is not known whether more will be made.

AmigaOS 4 is still under development, and reports are that it is quite stable and usable. It is hoped that it may be ported to other hardware, possibly another evaluation board, the Pegasos or some kind of Cell based device.

Trivia

• The name amiga is the Spanish and Portuguese word for "female friend", from the Latin amica.
• The Amiga still has a very strong user community, particularly outside the United States.
• The TV game show Lingo from 1987 used the Amiga computer for the Lingo cards and the randomly selected five-letter words.
• Much operating system advocacy surrounds the technology implemented in the Amiga. This leds some to accuse Amiga users of zealotry (look for "Amiga Persecution Complex" in the Jargon File).
• Amiga's three-finger salute, (CTRL plus the two "Amiga" keys), which reboots the system (but doesn't erase or reload the kickstart software) is actually implemented in hardware, unlike the software-based forms in many OSs. Newer Amigas introduced software-handling of the sequence, but if the OS software doesn't acknowlege the key sequence in a short time (perhaps because the OS has crashed), the keyboard hardware will forcibly reset the CPU. Another kind of three-finger salute (CTRL plus the two "Alt" keys) was introduced with AmigaOS 4.0.
• When AmigaOS crashes, it displays a flashing red box with a mysterious Guru Meditation number — two 32-bit hexadecimal values. The number is usually the 68000 exception number or one of a list of error numbers, and some other piece of information, such as the address of the task that was running at the time the crash was detected.
• During the Commodore era, machines with "thousands" model numbering were marketed as "quality" machines for business use, while the other machines (A500, A500+, A600, A1200) were "consumer" machines.
• The three most popular low-end models of the Amiga - the 500, 600 and 1200 - each have the name of a B-52's song written on their motherboard. The most widely cited reason for this is the designers having been fans of the band. The motherboard of the 500 says "Rock Lobster", that of the 600 says "June Bug" and that of the 1200 says "Channel Z". No other models have song names on their motherboards.
• Steve Jobs was shown the original prototype for the first Amiga (Amiga 1000) before it had been purchased by Commodore, and said there was "too much hardware". He was working on Macintosh at the time.
• Two of the designers of the original Amiga, RJ Mical and Dave Needle, would later go on to design the Atari Lynx, giving it a framebuffer based display with a blitter very similar to that in the Amiga. The two would also go on to work on the 3DO Interactive Multiplayer.
• When Great Valley Products first released their 68030 accelerator board for the Amiga 2000, it ran Apple's MacOS faster than any real Mac. Apple soon caught up, though.
• In 1999 an announcement was made claiming that a German company named iWin was designing new computers that were compatible with both classic Amigas and IBM PCs. The only source of information about these computers was iWin's own website, which contained some technical circuit diagrams about them. Upon closer inspection, the circuit diagrams were revealed to be completely unrealistic. After a few months, the supposed "iWin Amigas" vanished without a trace, without ever being publicly presented or released into the mass market. The general consensus of the Amiga community is that iWin never had done any real design, but were simply trying to pull a hoax on the eagerly-awaiting Amiga fans.

See also

• AmigaOS
• Amiga software
• Amiga emulation
• Unix Amiga Emulator
• SCA virus
• Gateway 2000
• List of arcade games ports to Amiga

References

• John J. Anderson, "Amiga Lorraine: finally, the 'next generation Atari'?" Creative Computing, April 1984
• Dave Haynie. "The Amiga A3000+ System Specification". 1991 DevCon Release. July 17, 1991.
• Bagnall, Brian (2005) On the Edge: The Spectacular Rise and Fall of Commodore. Variant Press, ISBN 0973864907.

External links

News and discussions

• Amiga.org
• Amigaworld.net - Official support forum for the AmigaOne.
• ANN
• Moo Bunny - Open discussion about Amiga and other computing related topics
• Obligement - magazine about AmigaOS and MorphOS.
• ClassicAmiga.com - Amiga game database and discussion forum.
• Lemon Amiga - A friendly Amiga community mostly focusing on games.
• Abime.net - Amiga addicts sanctuary, an Amiga community.
• The Amiga Zone - Amiga emulation and discussion forum.

Software

• - Official AmigaOS4.0 website
• AmigaOS - Unofficial AmigaOS Support Homepage
• Aminet - Public domain and freely available software for AmigaOS.
• OS4Depot - Unofficial repository for AmigaOS 4.x software.
• Amiga.sf - Your source to Amiga ports.

Links directory

• A big Amiga web directory

Link pages

• Amiga Realm - Amiga Internet Directory Service and Archive Resource.

History

• Amiga History Guide
• The History of the Amiga
• Amiga.org links

Other

• Amiga Music Preservation - All about the Amiga Audio/Module/Protracker/Mods/Modules scene.
• AmigaOne Productions Videos of Amiga group meetings and OS4 demonstrations.
• Amiga Wiki
• BLAZEMONGER - Amiga humor.
• Pouet - A demoscene portal.
• Amiga Demoscene Archive - Demoscene portal entirely dedicated to Amiga.
• The Big Book of Amiga Hardware
• The Software Preservation Society - Dedicated to the preservation of classic software for the Amiga and other platforms.
• The Amiga Hardware Database - Collection of Amiga hardware expansions and the Amiga models.
• Jim's Amiga Commercial Page! - Watch original Amiga commercials.
• Hall Of Light - The database of Amiga games.
• AmigaMemo - Amiga Game Museum.
• PowerUP - Unofficial PowerUP Support Homepage.
• G-Rex PCI - Unofficial G-Rex PCI Support Homepage.
• AmigaNostalgia - Retro software for all your emulation needs.
• Amiga Animations - A collection of classic animations created with the Amiga.

• Home computers
• Personal computers
• Commodore Amiga
• CBM hardware