Chapter I - Introduction
CHAPTER 1 INTRODUCTION The Amiga Personal Computer is a low-cost, high-performance system with advanced graphics and sound features. We call it the world's first personal supercomputer. That's a strong statement but one that is substantiated by the Amiga's capabilities. This chapter contains a brief overview of the Amiga PC hardware, a guide to the rest of this manual, and a system-wide glossary. The first part of the hardware overview describes all of the physical hardware modules, and the second part briefly summarizes the functions of the special purpose graphics and audio hardware and how it interacts with the main processor.
1. PHYSICAL HARDWARE MODULES Here is a list of the physical hardware components of the Amiga Personal Computer. - Motorola 68000 16/32-bit main processor - 256K bytes of internal RAM, user-expandable to 512K, in a 16-megabyte contiguous space (external expansion also available) - 192K or ROM containing a real-time, multi-tasking operating system with sound, graphics, and animation support routines - A built-in 3-1/2 inch double-sided disk drive. Disks are 80-track, double-sided, formatted as 11 sectors per track, 512 bytes per sector (over 900,000 bytes per disk). - An expansion disk port for connecting up to 3 additional disk drive units. The disk drives may be either 3-1/2 inch or 5-1/4 inch, double sided. - A fully programmable serial port allowing baud rates of beyond 31250 baud - A fully programmable parallel port. Normally, the port is configured as a Centronics [tm] parallel printer output, or it can be used as a high-speed parallel input port. - A two-button opto-mechanical mouse - Two reconfigurable controller ports (for mice, joysticks, paddles, or custom controllers) - A detached 89-key keyboard with calculator pad, function keys, and cursor keys - Ports for simultaneous NTSC, composite video, and analog or digital RGB output - Ports for audio output to left and right stereo channels from 4 special-purpose audio channels - An expansion connector for adding such accessories as RAM, additional floppy or hard disk drives, peripherals, or coprocessors
2. HARDWARE INTERACTION If the previous list of hardware features alone is not enough to distinguish the Amiga PC from other personal computers, then this section should convince you that the "personal supercomputer" claim is justified. This description of the way the Amiga's hardware elements work together will show how the Amiga provides a unique blend of versatility and raw performance.
The 68000 The Motorola 68000 is a 16/32-bit microprocessor operating at 7.1 megahertz. In the Amiga PC, the 68000 can address over 8 megabytes of contiguous random access memory (RAM). The 68000 shares the lowest half-megabyte of RAM space with the Amiga's special-purpose graphics and sound direct memory access (DMA) hardware. Both the 68000 and the special-purpose hardware can read and write into this lowest-address memory region. Performance for the 68000 is enhanced by a system design that gives it every alternate bus cycle, allowing to run at full rated speed most of the time. As described in the section below, the special-purpose hardware can steal time from the 68000 for jobs it can do more efficiently than the 68000. Even then, such cycle stealing only blocks the 68000's access to the shared memory. When using ROM or external memory, the 68000 always runs at full speed.
The Special-Purpose Hardware Among other functions, the special-purpose hardware provides the following features. - bit-plane generated high-resolutions graphics typically producing 320 by 200 non-interlaced displays, 320 by 400 interlaced displays, and 640 by 200 (non-interlaced) or 640 by 400 (interlaced) displays in 32 colors, or 16 colors. A special low-resolution mode is also provided, allowing you to have 4096 colors on-screen simultaneously. - a custom display coprocessor, allowing changes to any of the special-purpose registers in synchronization with the movement of the video beam. This allows such special effects as mid-screen changes to the color palette, splitting the screen into multiple horizontal slices, each having different video resolutions and color depths, beam-synchronized interrupt generation for the 68000, and more. The coprocessor can trigger many times per screen. It can trigger in the middle of lines, as well as at the beginning or during the blanking interval. The coprocessor itself can directly affect all of the registers of the special-purpose hardware, freeing the 68000 for general purpose computing tasks. - 32 system color registers, each of which contains a 12-bit number as 4 bits of RED, 4 bits of GREEN, and 4 bits of BLUE intensity information. This allows a system color palette of 4096 different choices of color for each register. Although an RGB monitor provides the best available output for the system graphics, test, and color, the NTSC signal has been carefully designed to provide maximum NTSC compatibility. This signal may be videotaped or fed to a standard composite video monitor. - 8 reusable 16-bit wide sprites with up to 15 color choices per sprite pixel element (when sprites are paired). A sprite is an easily movable graphics object whose display is entirely independent of the background (called a playfield); sprites can be displayed "over" or "under" this background. A sprite is 16 low-resolution pixels wide and an arbitrary number of lines tall. After producing the last line of a sprite on the screen, a sprite processor may be used to produce yet another sprite image elsewhere on-screen (with at least one horizontal line between each reuse of a sprite processor). Thus, you can produce many, many small sprites by simply using the sprite processors appropriately. - dynamically-controllable inter-object priority, with collision detection. This means that the system can dynamically control the video priority between the sprite objects and the bitplane background (playfields). You can control which object or objects appear "on top" at any time. Additionally, you can use system hardware to detect collisions between objects and have your program react to such collisions. - custom bit-blitter used for high speed data movement, adaptable to bit-plane animation. The blitter has been designed to efficiently retrieve data from up to 3 sources, combine the data in one of 256 different possible ways, and optionally store the combined data in a destination area. This is one of the situations where the 68000 gives up memory cycles to a DMA channel that can do the job more efficiently. The bit-blitter, in a special mode, draws patterned lines into rectangularly organized memory regions at a speed of about 1 million dots per second; and it can efficiently handle area fill. - audio consisting of 4 low-noise digital channels with independently programmable volume and sampling rate. The audio channels retrieve their control and data via direct memory access. Once started, each channel can automatically play a specified waveform without further processor interaction. Two channels are directed into each of the two stereo audio outputs. The audio channels may be linked together if desired to provide amplitude or frequency modulation or both forms of modulation simultaneously. - DMA-controlled floppy disk read and write on a full-track basis. This means that the built-in disk can read something over 5.6K bytes of data in a single disk revolution (11 sectors of 512 bytes each). All of the special functions described above are produced by three custom-designed VLSI circuits, which work in concert with the 68000. These circuits and the 68000 use the shared memory on a fully interleaved basis. That is, in order to run at full speed, the 68000 only needs to access the memory bus during each alternate clock cycle. During the rest of the time the 68000 performs some internal operation, leaving the memory bus free for other activities. The special-purpose hardware uses the memory bus during these free cycles, effectively allowing the 68000 to run at full rated speed "most of the time". The phrase,"most of the time" is quoted since there are some occasions when the special-purpose hardware steals memory cycles from the 68000, but with good reason. Specifically, the coprocessor and the data-moving DMA channel known as the blitter can each steal time from the 68000 for jobs they can do better than the 68000. Thus, the system DMA channels are designed with maximum performance in mind, where the job to be done is performed by the most efficient hardware element available. Another primary feature of the Amiga hardware is the ability to dynamically control which part of memory is used for the background display, audio, and sprites. The Amiga PC is not limited to a small, specific area of RAM for a frame buffer. Instead, the system allows display bitplanes, or sprite-processor control lists, coprocessor instruction lists, or audio channel control lists to be located anywhere within the lowest 512K of the memory map. The same region of memory can be accessed by the bit-blitter. This means, for example, that the user can store partial images at scattered areas of memory and use these images for animation effects by means of rapid replacement of on-screen material while saving and restoring background images. VCR and Direct Camera Interface In addition to the connections for NTSC composite Amiga video, and both digital and analog RGB monitors, the system can be expanded to include a VCR or camera interface. This system is capable of synchronizing with an external video source and replacing the system background color with an external image. This allows for the development of fully integrated video images with computer-generated graphics. Laser disk input is accepted in the same manner. System Expandability and Adaptability Expansion of the system hardware is easy. Peripheral devices are added to the system by attaching them to an expansion connector. You can add external RAM on the same expansion connector or upgrade internal RAM to 512K. Additional disk drive units may be daisy-chained from a connector at the rear of the unit for a total of 3 extra drives. The system software, as well, is highly adaptable to other host operating systems. The Amiga's graphics support routines are designed to make the user interface as friendly as possible. New peripheral devices are recognized and used by system software through a well defined, well documented linking procedure. The combination of power, low cost, versatility and expandability described here qualifies the Amiga Personal Computer as the world's first "personal supercomputer".
3. WHERE TO FIND INFORMATION IN THIS MANUAL This section is a roadmap to this manual and other Amiga manuals, showing you where to find the information you need. Here is a listing of where to look in this manual to find information about the hardware topics you have been reading about in this chapter. Peripheral devices Reading the I/O ports - chapter 8. Disk controller - chapter 8.
Bit-plane graphics In playfields - chapter 3.
Display coprocessor General description - chapter 2. Video beam postion detection - chapter 7.
Interrupts - chapter 7.
System color registers
In sprites - chapter 4. In playfields - chapter 3. Background color - chapter 3.
Movable sprite objects
Forming and displaying - chapter 4. Video priorities in relation to other objects - chapter 7. Collision detection - chapter 7.
Inter-object priority Between sprites and playfields - chapter 7.
Blitter animation In general - chapter 6. Blitter interrupts - chapter 7.
Line drawing and area filling Chapter 6.
Audio
In general - Chapter 5
Audio interrupts - Chapter 7 Audio output connections - Chapter 8
Disk read and write Chapter 8
DMA Effects of graphics operations on system DMA - Chapter 6. DMA control - chapter 7
Hardware expansion Chapter 8.
Interrupts In general - chapter 7.
These other Amiga manuals contain information related to the topics in this manual: Amiga ROM Kernal Manual This manual contains information about how the operating system works, including device support and libraries. Among other things, it shows you how to use the pre- written C language routines to produce applications featuring graphics, animation, and audio. Intuition User-Interface Manual This manual describes the user's interface to both the operating system and application programs. You can use Intuition's extremely versatile windows, screens, icons, menus, messages, and other features to customize how users will interact with your applications.
You may also with to refer to the following manuals: AmigaDOS Programmer's Manual AmigaDOS User's Manual AmigaDOS Technical Manual
4. GLOSSARY Here is a system-wide glossary that contains terms as well as terms introduced in other Amiga manuals. (The system-wide glossary goes here.)
