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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.

 

Contents

 

 

 

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.

 

 

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, 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. It never became truly mainstream, and (somewhat arguably) became obsolete in 1994 when Commodore International, its manufacturer, ceased operations.

 

CPU

 

The very first model, the Amiga 1000, had a 7.14 MHz 68000 CPU, designed to be capable of working directly with NTSC video. The CPU clock frequency was precisely double the 3.57 MHz color carrier frequency. Though most users attached an analog RGB monitor and most units even were sold together with an A1080/1/2 RGB-Monitor, the A1000 also had a built-in composite video output which allowed the computer to be connected directly to a TV or VCR. However, the output signal was considered too "hot" (strong) by many to be useful for anything other than home use. This could be remedied by running the A1000's composite output through a video processing amplifier, or "proc amp", to bring the video levels down to a suitable level.

 

Custom chipset

 

The Original Amiga chipset, or OCS, was more advanced than other architectures of its time: it had dedicated chips for real-time video effects, allowing users to easily work with genlocks to overlay graphics atop live video. The Amiga's unique overscan feature, the ability to run at custom, user-defined resolutions, allowed it to draw images past the visible borders of a television screen, allowing seamless fly-ins and scrolling from off-frame.

 

The machine was extremely expandable, supporting a huge amount of memory for the time. The original machine shipped with 256K (and was quite usable), and offered an initial expansion to 512K. That first 512K of memory was Chip RAM, which meant it was shared between the custom chipset and the CPU, with the chipset having priority. Additional RAM, up to 8 more megabytes, could 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 close to $10,000 US.

 

The Amiga had no text mode, offering only bitmapped graphics. It used 'planar' graphics, meaning that display memory buffers were 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 doubled the number of available colors. Low-resolution modes supported up to 5 planes (and, thus, 32 colors), while high-resolution supported 4 (16 colors). Each color could be chosen from the system palette of 4,096. This planar arrangement was a bit tricky to manipulate with the CPU, because any given pixel on the screen could be represented by up to 5 disparate bytes in memory. The blitter, fortunately, could handle most of this automatically.

 

To get around some of the color limitations, the Amiga also offered a unique HAM (Hold And Modify) graphics mode. In this low-resolution mode, a pixel could be any of the 32 basic colors, exactly like regular low-res screens. In addition, a given pixel could H)old the value from the previous pixel, and M)odify either the red, green, or blue value. Once software was developed that could encode images this way, a striking set of amazingly realistic still pictures began circulating. This mode was hard to program, and was mostly used only for slideshows and video overlays.

 

The video chipset was highly flexible, and was able to double the basic resolution of the screen by switching to interlaced mode. This was 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.

 

In addition, it could define and use arbitrary resolutions, drawing the extra pixels, if any, into the 'overscan' area around the borders of the screen. This let it shift quickly and easily between NTSC and PAL resolutions; the exact same hardware was sold in both areas. By specifying large overscan values, it could go past the borders of nearly all televisions. This allowed it to 'fly-in' objects from off-frame, and was absolutely crucial to its success in the video market.

 

Many users liked the higher-resolution display offered by interlace, but despised the flicker. 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 Amiga's unique architecture, however, was something of a drawback in high resolution modes. When displaying more than four colors in hires, the chipset required progressively more memory bandwidth. At 16 colors, it slowed 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 expansion became routine. High resolution did not slow access to CPU-only RAM. This led to its common name of "fast" RAM, as opposed to the "chip" RAM that could be seen (and slowed down) by the graphics subsystem.

 

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

 

The blitter

 

The blitter (block image transfer hardware) allowed the rapid copying of video memory, meaning that the CPU could be freed for other tasks. This was the beginning of modern-day graphics implementations, where dedicated GPUs (graphics processing units) operate independently of, but under instruction from, the CPU. The blitter therefore allowed a programmer to create bobs (blitter objects) that were controlled by subroutines under interrupt control. The main thread of the program was not used to perform the actual redrawing of the screen.

 

The blitter could also draw single-pixel thickness lines, and fill large areas with uniform or stippled colour, such as when 'blanking' the screen (clearing the screen in order to draw it again) or drawing 3D polygons. The blitter was never improved to be able to rotate or zoom bobs, or to apply textures to polygons. When these graphics techniques became commonplace (such as with the release of the SNES and Voodoo/ATI Rage-class graphics accelerators), the Amiga chipset dated rapidly.

 

The copper

 

The copper was a relatively simple chip that executed a programmed instruction stream, closely linked to the video hardware. It could do two fundamental things; 'wait' and 'move'. Wait simply delayed until a specific screen position was reached. Move could write arbitrary values into the chipset, which allowed, for instance, instantaneous palette changes mid-screen.

 

This also allowed the "re-use" of sprites. The Amiga's hardware engine supported only 8 sprites, but with copper support, could present the illusion of many more. Each sprite was drawn in a certain position, until the raster beam had passed it; the copper could then instantly change its location and appearance, moving it below the raster beam again. A single hardware sprite could thus serve as several visible objects on screen. It required CPU time to set up the copper lists, but actually moving the sprites was handled entirely in-chipset.

 

A similar technique offered one of the Amiga's most unusual features; the ability to actually change display resolutions and colour palettes on the fly — the computer could change resolution between scan lines, allowing for different horizontal resolutions to be displayed on the same screen. This was somewhat similar to the ability of Windows 95 and later machines to alt-tab between full-screen programs, but on the Amiga, users simply dragged the front screen down to see the one behind it.... both were visible simultaneously.

 

As technically fascinating as this was, the actual practical uses were limited. Paint programs used the feature to allow users to draw directly on a (low-resolution) HAM screen, while offering a high-res, detailed toolbar at the top or bottom of the screen. It could be used as a convenient way to watch the status of a full-screen program while doing something else in the foreground. It served as an excellent demonstration of the machine's graphic prowess. Beyond that, it was largely a curiosity.

 

Late in the Amiga's evolution, an advanced copper technique was invented: Sliced HAM, or S-HAM. This consisted of writing a very dense copper list, which switched the palette on every line of a HAM display, removing most of that mode's color limitations. This was a large jump in image quality, but it required nearly all the resources of an OCS machine simply to display an image. The fact that it could be done at all was a testament to the amazing power and flexibility of the chipset.

 

Video applications

 

Today, many TV stations and broadcast corporations are still using A3000s and A4000s for their real-time video effects. Many programs were also written for creating "fansubs" of foreign films and Japanese animation. Many competing products were created for the Amiga's video capabilities ranging from simple genlocks that allowed you to simply switch the RGB overlay feed on and off, to more advanced devices like the Supergen which had faders, and the ultimate expression of the Amiga's native power, the Newtek Video Toaster. Other interesting products that used the genlock capability enabled 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 had 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 required the camera to accept a sync pulse from the computer, so they were 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 meant that not only could the Amiga produce computer-generated images and sound, but users could input "real" images and sound for editing, composition, and use in computer games.

 

 

Sound

 

The original sound chip supported 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 was 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 used software mixing to allow 8 or more virtual channels, and astute composers could 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 was 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 were developed 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 were 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 were 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 were memory, SCSI controllers and CPU accelerator cards. These were sometimes combined into the one device, particularly on big box Amigas like the A2000, A3000 and A4000.

 

Early CPU accelerator cards featured 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 featured the 68040 and 68060. Both CPUs featured integrated FPUs and MMUs. Many CPU accelerator cards also featured 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 was usually used as a coprocessor for heavy computations (a powerful CPU was needed to run for example MAME, but even decoding JPEG pictures and MP3 audio was considered heavy computation in those years). It was 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 were also available 24 bit graphics cards and video cards. Graphics cards were designed primarily for 2D artwork production, workstation use, and later, gaming. Video cards were designed for inputing and outputting video signals, and processing and manipulating video.

 

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

 

Various manufacturers started producing PCI busboards for the A1200 and A4000. These allowed PCI cards to be used in standard Amigas offering access to such delights 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, new generations have been produced, including the PPC based AmigaOne. In addition, some companies released unofficial Amiga clones.

 

 

Amiga emulators

 

 

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

 

Operating systems

 

AmigaOS

After powering up or rebooting an Amiga 500 this screen display is seen, meaning the OS has started and is asking the user to insert a bootable floppy disk. The displayed OS is Kickstart 1.3.

After powering up or rebooting an Amiga 500 this screen display is seen, meaning the OS has started and is asking the user to insert a bootable floppy disk. The displayed OS is Kickstart 1.3.

 

The operating system that is now known as AmigaOS initially consisted of two components - Kickstart and Workbench. Kickstart was a collection of function libraries functionally equivalent to BIOS but with floating-point maths routines, device driver APIs, and more. Workbench was the name of a collection of utility programs contained on a floppy disk.

 

AmigaOS was also quite sophisticated for its time, combining an intuitive graphical user interface (GUI) like that of the Apple Macintosh together with an elegant Command Line Interface (CLI) which then eventually evolved into a very powerful Shell. This gives the user of Amiga some of the flexibility of Unix while retaining a simplicity that made maintenance rather easy. While its operating system was the only preemptive multitasking platform with an efficient message-passing kernel in the consumer marketplace for several years with an efficient memory management, robustness left something to be desired, mainly due to the absence of protected memory, resulting in the famous "Guru Meditation" errors.

 

Programmers made certain assumptions about undocumented behaviour of Kickstart 1.x (such as the fact that jumping to the start of the ROM code would perform a hot reset). Kickstart 2.0 initially caused widespread software incompatibilities. Commodore created kludges within the operating system to mimic the behaviour of previous machines so that those assumptions would continue to hold true.

 

With the release of Workbench/Kickstart 2, the powerful scripting language AREXX was integrated into the OS and provided with the OS. AREXX is based on REXX, and provides facilities similar to Visual Basic in Windows, such as interprocess communication. AREXX added to the customisable nature of AmigaOS. Workbench 2.1 introduced locale as well as CrossDOS, which enabled the OS to read MSDOS formated Disks. Workbench 2.1 worked on the 2.0 kickstart.

 

Workbench 3.0 introduced Datatypes, aswell as support for the AGA chipset. 3.1 added integrated suport for CD-ROMs. 3.5 and 3.9 added many features such as MUI and networking, which were previously third party add ons.

 

The Amiga operating system was resurrected in 2000 as AmigaOS 4, which currently runs only on AmigaOne computers and on A1200s and A4000s with a PowerPC accelerator card.

 

AmigaOS 4 is still in beta stage and is a full port of the OS to PPC. It also improves on many of the features introduced in 3.5 and 3.9. It features limited emulation of classic hardware such as the 68000 CPU. It will run legally coded Classic applications which do not rely on the presence of classic hardware (such as the AGA chipset). A version of UAE called e-UAE is available for AmigaOS4 for running those programs which rely on classic hardware.

 

*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 was an official, older version of OpenBSD. The last Amiga release was 3.2.

 

 

The bootblock

 

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

 

However, subsequent Amigas held Kickstart in a ROM chip. When the machine was started, Kickstart would display 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) would be loaded into RAM and control was passed to it.

 

Most recreational software, especially during the Kickstart 1.* years, would contain a bootblock that loaded the rest of the software from the disk and then pass control to it. The game or demo would then summarily take control of memory and resources to suit itself, effectively disabling AmigaOS. The GUI would never be invoked. Therefore, most games and demos did not use the operating system at all. Alternatively, it could be said that they installed 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 might 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, was known as a "DOS disk".

 

The bootblock became an obvious target for virus writers. Custom bootblock loaders were then created, which displayed messages such as "Your disk has no virus" before loading the dos.library. If one installed a DOS bootblock (or a virus surruptitiously installed itself) onto a custom disk, it would ruin the software.

 

 

Emulation

 

 

The Amiga was able to emulate other computer platforms in its same price range, most notably the IBM PC and the Apple Macintosh. There were 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) was 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 was considered by some to have had 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. There were many fans who believed that the Amiga was unique and was better than other platforms - some still exist to this day using the AmigaOne (manufactured by UK firm Eyetech), despite utilising slower hardware compared to a PC of the same price.

 

One reason for this loyalty was due to the strengths of the machine at the time: it had a stable, compact, efficient, multitasking OS, it was relatively easy to program for, software had relatively easy access to the hardware (the base hardware was fixed so software could be coded specifically to the hardware), there was 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 continued to produce software and get as much as they possibly could out of the machine. Amiga users managed 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' continued for 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, released a limited number of AmigaOne's. This was a new motherboard based on MAI's Teron POP (PowerPC Open Platform) based designs, and was made to run AmigaOS 4. The original G3 based motherboard, was replaced with a newer design with a replacable CPU module which came in G3 and G4 flavours. In 2004 a micro ATX model with a 750GX G3 CPU was released. Because of the AmigaOne's radical departure from previous Amiga designs with their custom chipsets, the older machines are often referred to as Classic Amigas, to distinguish them from the PPC based AmigaOnes.

 

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

 

 

 

See also

 

 

 

References

 

 

 

 

External links

 

News and discussions

 

 

 

Software

 

 

 

Links directory

 

 

 

Link pages

 

 

 

 

History

 

 

 

 

Other

 

 

M68K-based (16/32-bit): Amiga 1000 Amiga 500 Amiga 2000 Amiga 500+ Amiga 2500 Amiga 3000, UX, T Amiga 600 Amiga 1200 Amiga 4000

 

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