Top Document: Atari 8-Bit Computers: Frequently Asked Questions Previous Document: 0.1) Table of contents Next Document: 1.2) What is the Atari 400? See reader questions & answers on this topic! - Help others by sharing your knowledge Based in Silicon Valley in the U.S.A., the company known as Atari produced a line of home computers from 1979 to 1992 often referred to collectively as the "Atari 8-bits," the "8-bit Ataris," the "400/800/XL/XE series," etc. The computers included the 400, 800, 1200XL, 600XL, 800XL, 65XE, 130XE, 800XE, and the XE video game system. Notable home computers that were introduced before the Atari 400/800: 1977: Apple II, Tandy Radio Shack TRS-80 (Model I), Commodore PET Notable home computers that were introduced after the Atari 400/800: 1979: Texas Instruments TI-99/4 1980: Commodore VIC-20, TRS-80 Color Computer, Osborne 1 1981: Texas Instruments TI-99/4A, IBM PC, Sinclair ZX81 / TS 1000, BBC Micro 1982: Kaypro II, Sinclair ZX Spectrum, Commodore 64 1983: Coleco Adam, MSX 1984: Apple Macintosh, Amstrad CPC 1985: Atari ST, Commodore Amiga 1987: Acorn Archimedes In marketing their computers to the public, Atari always had to contend with their company history and reputation as a maker of video games. While the 8-bit Atari computers in their heyday were technically quite comparable if not superior in the worlds of home and business personal computing, they also live up to the name "Atari" with a huge library of video games which were often outstanding for their time. The 8-bit Atari computers do not use the same cartridges or floppy disks as any other Atari platforms, such as the 2600 Video Computer System (VCS), the 5200 SuperSystem, the 7800 ProSystem, or the ST/TT/Falcon computers. All of these but the 5200, however, do share the same joystick/controller hardware port. The 5200 SuperSystem is actually nearly identical to the 8-bit computers internally, yet cartridges for the 5200 and the 8-bit computers cannot be exchanged, primarily due to the physically different cartridge ports. Here are some of the performance specifications of the 8-bit Atari computers: CPU: 6502B (most 400/800 machines), or Atari SALLY 6502 (late 400/800 machines and all XL/XE machines) CPU CLOCK RATE: 1.7897725 MHz (NTSC machines), or 1.7734470 MHz (PAL/SECAM machines) FRAME REFRESH RATE: 59.94 Hz (NTSC machines), or 49.86 Hz (PAL/SECAM machines) MACHINE CYCLES per FRAME: 29859 (NTSC machines) (1.7897725 MHz / 59.94 Hz), or 35568 (PAL/SECAM machines) (1.7734470 MHz / 49.86 Hz) SCAN LINES per FRAME 262 (NTSC machines), or 312 (PAL/SECAM machines) MACHINE CYCLES per SCAN LINE 114 (NTSC machines: 29859 cycles/frame / 262 lines/frame) (PAL/SECAM machines: 35568 cycles/frame / 312 lines/frame) COLOR CLOCKS per MACHINE CYCLE 2 COLOR CLOCKS per SCAN LINE 228 (2 color clocks/machine cycle * 114 machine cycles/scan line) MAXIMUM SCAN LINE WIDTH = "WIDE PLAYFIELD" 176 color clocks MAXIMUM RESOLUTION = GRAPHICS PIXEL 0.5 color clock MAXIMUM HORIZONTAL FRAME RESOLUTION 352 pixels (176 color clocks / 0.5 color clock) MAXIMUM VERTICAL FRAME RESOLUTION 240 pixels (240 scan lines per frame) GRAPHICS MODES: ANTIC GTIA CIO/BASIC Display Resolution Number of Mode # Mode # Graphics # Type (full screen) Colors/Hues ---------------------------------------------------------------------- 2 0 Char 40 x 24 1 * 3 - Char 40 x 19 1 * 4 12 ++ Char 40 x 24 5 5 13 ++ Char 40 x 12 5 6 1 Char 20 x 24 5 7 2 Char 20 x 12 5 8 3 Map 40 x 24 4 9 4 Map 80 x 48 2 A 5 Map 80 x 48 4 B 6 Map 160 x 96 2 C 14 ++ Map 160 x 192 2 D 7 Map 160 x 96 4 E 15 ++ Map 160 x 192 4 F 8 Map 320 x 192 1 * +F 1 9 Map 80 x 192 1 ** +F 2 10 Map 80 x 192 9 +F 3 11 Map 80 x 192 16 *** * 1 Hue, 2 Luminances ** 1 Hue, 16 Luminances (GTIA); or, 1 Hue, 8 Luminances (FGTIA) *** 16 Hues, 1 Luminance + require the GTIA/FGTIA chip. (1979-1981 400/800's shipped with CTIA.) ++ Not available via the BASIC GRAPHICS command in 400/800 version of OS. (See a separate section in this FAQ list for a discussion of the "missing" ANTIC Modes 0 and 1.) GRAPHICS INDIRECTION (COLOR REGISTERS AND CHARACTER SETS): Nine color registers are available. Each color register holds any of 16 luminances x 16 hues = 256 colors. (Four registers are for player-missile graphics. Character sets of 128 8x8 characters, each with a normal and an inverse video incarnation, are totally redefinable. PLAYER-MISSILE GRAPHICS: Four 8-bit wide, 120 or 240 byte high single color players, and four 2-bit wide, 120 or 240 byte high single color missiles are available. A mode to combine the 4 missiles into a 5th 8-bit wide player is also available, as is a mode to OR colors or blacken out colors when players overlap (good for making three colors out of two players!) Players and missiles have adjustable priority and collision detection. DISPLAY LIST: Screen modes can be mixed (by lines) down the screen using the Display List - a program which is executed by the ANTIC graphics chip every screen refresh. DISPLAY LIST INTERRUPTS (DLIs): Other screen attributes (color, player/missile horizontal position, screen width, player/missile/playfield priority, etc.) can be adjusted at any point down the screen via DLIs. SCROLLING: Fine scrolling (both vertical and horizontal) can be enabled on any line on the screen. SOUND: Sound is monaural/monophonic (one channel output). Up to 4 separate simultaneous voices can be produced, configured as one of the following: - 4 voices, each with one of 256 unique frequencies/pitches - 2 voices, each with one of 65,536 unique frequencies/pitches - 1 voice with one of 65,536 pitches and 2 voices with one of 256 pitches Each voice may be produced with one of 8 available "noise" settings/ polynomial-counter combinations, commonly called "distortion" settings. (There are actually only 6 distinct combinations of 3 poly-counters offered, but one of the poly-counters has 2 available settings itself, resulting in 2 additional noise settings for the total of 8 available.) Each voice may be produced at one of 16 volumes. Direct control of the position of the speaker cone is also available, with 4-bit (16 position) resolution. Known as "volume only mode" on the Atari. A fifth "voice" is produced as a separate signal by the internal speaker on the Atari 400/800. This is typically used only for keyclick and buzzer. In XL/XE systems these sounds are output as part of the normal monaural audio output signal. VERTICAL BLANK INTERRUPTS (VBIs): A software routine may be designed to execute as a VBI. There are two varieties of VBI: Immediate and Deferred. An Immediate VBI completes execution within the vertical blank time, which is the time allotted for a CRT display to shut the electron beam off at the lower-right of the display and reposition it back on the top-left of the display to commence drawing of the next frame. A Deferred VBI routine completes execution between the initiation of one vertical blank and the next. User Contributions:Top Document: Atari 8-Bit Computers: Frequently Asked Questions Previous Document: 0.1) Table of contents Next Document: 1.2) What is the Atari 400? Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: Michael Current <michael@mcurrent.name>
Last Update March 27 2014 @ 02:11 PM
|
Comment about this article, ask questions, or add new information about this topic: