Classic Computer Magazine Archive CREATIVE COMPUTING VOL. 11, NO. 9 / SEPTEMBER 1985 / PAGE 32

Amiga; the message is the medium. (computer) (evaluation) John J. Anderson.

While the pro forma prophecies of the nerd wave poet and resident genius of the group Talking Heads are undoubtedly a tad overstated, there is at least one real point within them to be considered. That concerns the future of the computer not as mere number cruncher or problem solver, but as a medium of communication. I will not belabor an argument for the validity of the concept--because you are reading a copy of Creative Computing, I will assume you may be spared. You already know why a computer should feature great graphics and sound. You already know that no matter what machine you use, the promise of windows and menus is a worthy one. You already know that micros with output in the same range of sophistication and real-time involvement as television are where the future of creative computing will come to rest, and you can hardly wait.

Evolutionary War

A little over two years ago, two gentlemen from a small joystick company called Amiga paid us a call at the lab. David Morse and David Reisinger had no more than a pitch and a slideshow to show us, but we were impressed by their savvy and their sincerity. They spoke of a custom chipset from Jay Miner, the man who designed the Atari 400/800 chipset. They spoke of graphics and sound of a quality yet unimagined in a personal computer. They spoke of a commitment to an MPU that allowed true multitasking and RAM in excess of 5Mb. I broke the story of the Amiga computer, then code-named Lorraine, to the world back in early 1983.

Time passed, and at successive Consumer Electronics Shows, I viewed the progress of the Amiga. It was a room full of breadboards, then a table full. It was driven by a mini-computer development system, then by a PC. ROM dates slipped and slipped and slipped, but finally the Amiga existed in a single breadboard unit with three custom VLSI ROMs socketed upon it. Now, after one of the most excruciating waits in the industry, not to mention acquisition (for $25 million) by Commodore, the Amiga computer is ready.

Hardware Specs

The Amiga is based on the Motorola MC 68000, which is a 16-bit processor with many attributes of a 32-bit MPU, capable of a cycle rate of 7.8MHz. It ships with 256K of RAM expandable to 512K onboard and up to a whopping 8Mb externally. It also holds 192K of ROM and real-time multitasking operating system with a bevy of sound, graphics, animation, and housekeeping support routines.

In addition, as standard equipment the Amiga sports an internal 3.5" dualsided microfloppy disk drive capable of storing 880K per disk. The drives format disks into 80 tracks of 11 sectors per track, 512 bytes per sector. Reads and writes are DMA (direct memory access) controlled on a full-track basis. Drives are rated at up to a 5.6K read or write on a single revolution. Expansion is possible to three additional daisychained drives, including 5.25" drives.

The Amiga also ships with a fully programmable serial port, allowing speeds up to 31,250 baud, and a fully programmable parallel port, normally configured for the Centronics standard. There are ports for RGB, NTSC, and RF modulated video, as well as two controller ports and an expansion bus for RAM, additional floppies or hard disks, and other peripherals. Audio outputs are discussed ahead.

The keyboard is an 89-key fullstroke detached console with ten function keys, directional cursor keys, and a numeric keypad. Key layout is modified Selectric-style, with a decent, if slightly mushy, feel. One of the nice design features of the machine is the fact that the system unit is raised, allowing the keyboard to slide beneath it for storage.

The system unit is Apple biege, low-slung, with a footprint slightly smaller than that of the IBM PC. A cartridge slot in the front of the unit fits the internal RAM upgrade. On the righthand side of the box is the expansion bus, covered by a door when not in use, along with dual controller ports. All other connectors go into the rear of the system unit.

The Amiga comes with a two-button mechanical mouse, which feels good in the hand and moves the screen pointer crisply with a good feel. It plugs into controller port 1.

Three custom chips handle graphics, animation, sound, and I/O tasks that would otherwise tax the MPU greatly, achieving exceptional results. They work in concert with the 68000, "stealing" time on an interleaved basis. (For a technical overview of the custom chips and some of their potentials, see the sidebar.) Both the 68000 and the custom hardware can read and write to the lowest 500K of RAM. Processor speed is enhanced by the system design, which gives the MPU every alternate bus cycle, allowing it to run at full-rated speed most of the time.

The audio channels consist of four low-noise digital voices split into dual RCA phono plug outputs for use in generating stereophonic effects. Each voice can handle a range of nine octaves, with independent and fully programmable waveforms. The audio channels retrieve their control and data via DMA (direct memory access). Once set, each channel can automatically play a specified waveform without further interaction with the processor. Audio digitization is also possible. The digital sampling rate is fully programmable.

The Amiga can dynamically control which part of memory is used for background display, audio, and sprites, and is not limited to a small, specific area of RAM for screen memory. This allows display bitplanes (of which there are five), sprite-processor control lists, coprocessor instruction lists, or audio channel control lists to be located anywhere within the lowest 512K of the memory map. That same low portion of memory is also accessible to a mechanism called the "bit-blitter" (see sidebar), which can store partial images in scattered areas of memory. These images can then be used for animation effects by means of bit-mapped movement, while saving and restoring background images.

On the back panel of the Amiga is a video input along with multiple outputs. The machine is capable of synchronizing via an optional genlock interface with an external video source. The background color can then be replaced with the input still-frame image. This allows for the development of fully integrated video images with computer generated graphics.

Software Specs

Foremost on the software list of the machine is Intuition, the Amiga user interface. This is a group of system routines that manages a fully-featured windowing system of I/O, allowing flexible use of the true multitasking capability of the 68000 MPU across all graphics modes. Not only can multiple programs reside simultaneously in memory, but they can share system resources with one another. Intuition provides the user with a constant, convenient interface with the operating system and the programs that run within it. At the same time, Intuition provides the programmer with system resources that can run simultaneously with any other program, with no danger of one programming bombing the other or even stepping on its feet. The operant concept is that of a "virtual terminal," wherein each program runs on the equivalent of its own dedicated machine.

On a machine like the Apple Macintosh, there is a single bit-mapped graphics mode, and any type of window can be overlaid on any other. However, in a machine like the Amiga, where graphics modes may depend on complex interrupt-driven color scan techniques, problems are created where one graphics mode of window would be overlaid on another mode of window. The only windows that can cleanly overlay each other are those that share graphics specifications.

Intuition gets around these problems with a mechanism called "screens." These are distinct from windows in that they can be sized only vertically and can consist of one or more overlapping windows of a single specification. Horizontally, they are full-screen in size. Vertically they scroll just as do windows.

The default screen of Intuition is called Workbench, which is to the Amiga as Finder is to the Macintosh. It allows the user to interface with the operating system within a desktop metaphor, using the mouse to point and click between operations. Intuition provides system exec routines to handle the operation of the entire desktop with the following mechanisms:

* Menus: A complete menu manager.

* Gadgets: Control of windows and input types.

* Requesters: Information input pop-up box.

* Alerts: Information output pop-up box.

* Clipboard: A RAM-based byte stream for data transfer.

If you are not a believer in the desktop metaphor, you can toggle to CLI (command line interface) mode and control the operating system from a command prompt format extremely similar to that of MS-DOS. Amiga DOS is a multitasking program execution environment that is designed to create virtual terminals for all active programs. It supports synchronous and asynchronous I/O, a hierarchical filing system of directories and subdirectories, multiple volume support, device independent I/O, and a RAM disk. Its only limitations are available disk and memory space. It also supports a programmer's toolkit, designed to ease program development by providing access to the huge collection of service routines available in ROM.

Toward a New Medium of


There is not much use in trying to describe the Amiga much more than we already have, although we shall attempt to do so. The fact is that until you see and hear it in operation, you cannot know what it really is. Here, in as vivid a form as I can describe them, are some of the things I have seen and heard the Amiga do:

* A soccer ball bounces from left to right on the screen. It spins slowly on a tilted axis as it moves, showing the facets of its surface, changing the direction of spin when it hits a wall. It sounds just the way it should, unmistakably like a ball, rather than a computer imitating a ball. The ball and background are detailed, yet movement is swift and perfectly smooth.

* A detailed humorous, colorful street scene is populated by five blittered characters (not sprites). Each walks, glides, hops, or minces quickly in the correct priority (foreground character in front of background character). The characters are colorful and highly detailed, and even contain "transparent" parts you can see through. Obviously designed by a talented animation artist, the effect is uproarious.

* Multiple multicolored balls animate a collision pattern. Each makes use of sophisticated shading techniques for a shiny, metallic look. Rules governing the effects of collision create a kaleidoscopic, colorful effect--again moving fast but without flicker or jar.

* The keyboard of the Amiga is transformed into a professional synthesizer. Sound is on a par with a Yamaha DX-9. Waveforms run the gamut from banjo to electric guitar to instruments you have never heard before. Tunes can be played in real time or from data files.

* Highly intelligible synthesized speech can output in male or female voices. They pronounce unaltered English spellings with very few errors. Unlike synthesizers for other machines, this one does not require concentration to understand. And it can be called up as an exec from within any program.

* Digital sound of superlative quality recreates the sound of a basketball hitting a backboard, a car crash, squeaky sneakers, or a recognizable human voice. Though memory intensive, these effects can be read from disk very quickly.

The Downside

I have very few complaints about the Commodore Amiga, but that won't stop me from picking a few nits. I am unhappy with the tooling of the production Amigas I have seen. The plastic is a lightgauge polystyrene, and the pieces don't fit together as well as they should. Even the IBM PCjr case was of higher quality. Though the system unit is rated at a 40 lb. top load, it does not bespeak quality, as it should. The criticism also extends to the keyboard, which feels just a tiny bit loose. According to Clive Smith, marketing VP at Commodore, subsequent production runs will feature better tooling and a heavier case. He promises that the keyboard, too, will be improved.

I found the drives to be slow during certain operations. When loading a directory, for instance, they became a little bogged down. They are also a bit noisy. Smith assures me that these are both software problems that will be solved in production units.

The system lacks a clock. You must set the time and date, if you are interested in such things, every session at boot time.

I failed to find an AUTOEXEC command in DOS. This may have been an omission in the documentation. If however it is not, the possibility of autoboot files could be in question. What is more likely is that setting them will be a bit more work.

The RGB monitor connector is nonstandard. Unless you buy the Commodore monitor to be offered alongside the Amiga, you may be hard-pressed to find the DB-23 connector necessary to wire a custom monitor cable. Commodore will, however, market a generic cable for use with third-party monitors.

The version of Basic I saw lacks a screen editor. Two versions of Basic are planned: one from Microsoft and the other from MetacompCo, a British firm. I examined the latter, and among other things was disheartened by the fact that it lacked any sophisticated form of editor. I ran the Ahl benchmark, but the results were so disparate I cannot assign them any validity.

Part of the reason I'm such a curmudgeon is that I have such high hopes for the Amiga. Please rest assured that it is one hell of a magic box, and that the complaints I have made are largely cosmetic or picky or will be solved by upcoming options.

The real message to come away with is that the Commodore Amiga is a new communications medium--a dream machine. Its display is crystal clear--better than any I have ever seen, in any graphics mode. Its sound far surpasses that of any microcomputer that has come before. Its multitasking computing power and open-ended RAM capability make it a Herculean muscle machine. The expansion port with MPU bus leaves the future wide open for peripherals, including hard disks and CD-ROMs. Make no mistake about it: the Amiga may never inspire a religious experience in the user, but it can serve as the delivery vehicle for extremely sophisticated interactive experiences. And with its canned set of tools, it may come close to providing a religious experience for the programmer.

Products: Commodore Amiga (680X0-based system)