Atari 400 Home Computer (1979)

Features

CPU: MOS 6502 1.79MHz
Co-Processors: ANTIC (Scrolling, Sprites, Video), CTIA / GTIA (Color, Sprites, Collisions), POKEY (Timers, Sound, Keyboard, Serial I/O), PIA 6810 (I/O including controller ports)
RAM: 8K or 16K (newer models)
ROM: 10K
Display: 24 x 40 text, 320 x 192 monochrome, 160 x 96 with 128 colors
Expansions: 2 internal expansion slots, 1 cartridge slot under front cover and a daisy-chainable expansion bus
Ports: 4 controller ports
Keyboard: QWERTY membrane keyboard with 61 keys, 4 function keys (Reset, Option, Select, Start)
TV video output
Storage: external 5.25” floppy drive, cassette recorder
OS: Atari OS

Usage

Currently, MESS supports the following Atari 400 versions:

a400 [Atari 400 (NTSC)]
a400pal [Atari 400 (PAL)]

Both drivers support cart dumps in .rom and .bin format, using the “cartridge” (cart) device, and up to four floppy drive for disks in .atr, .dsk and .xfd format, “floppydisk1” (flop1) to “floppydisk4” (flop4).

Keyboard

These systems require full keyboard emulation to work correctly. At startup, full keyboard emulation mode is enabled by default. Whilst in full keyboard emulation mode, some key associated functionality may be disabled (like the ESC key for EXIT). The keyboard emulation mode is toggled using the “Scroll Lock” key (by default).

Original Keyboard: QWERTY, 61 keys plus 4 function keys on the right

CLEAR   INSERT   DELETE                   SYSTEM
  ESC    1!   2"   3#   4$   5%   6&   7'   8@   9(   0)    <        >     BACK S   BREAK            RESET
  
CLF  SET                                                     UP _    DOWN |
  TAB      Q    W    E    R    T    Y    U    I    O    P      -        =          RETURN           OPTION
  
                                                                LEFT \  RIGHT ^     CAPS
     CTRL    A    S    D    F    G    H    J    K    L     ;:      +        *       LOWR            SELECT
  
  
     SHIFT     Z    X    C    V    B    N    M    ,[     .]    /?     ATARI        SHIFT             START
  
  
                                   SPACE

Keys “TAB”, ”-”, ”=”, ”+” and “*” have 3 functions.

Known Issues

Most disk and cartridge images should work, though some graphic issues may exist. Note that the Atari 400 has less memory than the Atari 800, and some disk images may not work as a consequence; this is not a bug in the emulation.

History and Trivia

The Atari 400 and 800 were the first home computers to use custom coprocessors and the first to use “sprites” and special video interruptions like display lists, features that will be implemented several years after on the Commodore Amiga. It offered high graphic resolution, lots of colors and great sound capabilities, more than other computers could do then! The two models had same characteristics, the 400 is the low-cost version, it has only 16 KB (instead of 48 KB), one cartridge port (two for the 800) and a membrane keyboard (a typewriter style keyboard one for the 800).

Originally, the 400 was sold with 8 kb RAM, but later most 400's with 16 kb.

The Atari 400 was known inside Atari as code name “Candy”.

(info from old-computers.com)