atari 400


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(click on picture)


Introduced October 1979
Discontinued November 1983
Release Price     $599.99


        The year was 1978. Atari was at the top of the video gamming world with its 2600 VCS game console. Atari management looked around and saw a new and potentially lucrative market just beginning to take shape. This market was the Home Computer Market. They saw a market with relatively few major competitors and Atari was in a great position to market a computer of their own. They, after all, were a trusted household name, everyone owned an Atari or knew someone who did! 

       So December of 1978 Atari introduced the 400 and 800 series computers. The actual computers were not delivered until late 1979 due to production problems. 

       The 400 was a scaled down version of the Atari 800. Introduced as an entry level computer based on the same MOS Technology 6502A processor running at 1.70 MHz with 16K of user RAM built in. It had a membrane style keyboard (not very touch type friendly) with 62 touch sensitive keys and 4 special keys to the right of the keyboard. 

        It stood out amongst the other computer offerings of the day with its graphics and sound capabilities. It was capable of producing 128 colors on the screen using the CTIA video processor and up to 256 colors with the upgraded GTIA video processor chip used on later versions of the computer. The 400 was first amongst the early computers to be able to display 4 programmable screen objects simultaneously called 'Player-missiles' (also known as 'Sprites' on Commodore computers). This was at a time when the most computers produced only monochrome displays or very primitive 8 color screens. The graphics were handled by a custom chip called the "ANTIC" (CTIA/GTIA). This chip was designed to work as a sort of co-processor to take the work load away from the main processor to display graphics and color on the screen. 

       The team that developed the custom chips inside the 400 and 800 was headed by Jay Miner who later, after leaving Atari, headed the teams who developed the custom chips that surrounded the Motorola MC68000 processor that powered arguably the most advanced computer of its time, The Amiga 1000!

      The sound was supplied by another custom chip called "POKEY" and produced 4 voices for the most realistic sound production of any computer on the market at the time. Input/output was handled by a serial port on the right side of the machine. You could daisy chain a tape player, a 5 1/4 inch disk drive, a modem, or a printer through special d-type jacks. The Atari 400 could also accommodate up to 4 joysticks through ports on the front of the machine. The joysticks were of the standard type used on the 2600 VCS

      The computer was originally released standard with 16K of RAM, but unlike it's bigger brother it could not easily expand its RAM to 48K by plugging 16K RAM modules into the slots because it only had one slot. But inventive entrepreneurs soon found ways around this limitation and third party venders were soon selling expansion cards to replace the basic 16k card inside the 400 with larger ones.

     The Atari 400 was one of the few computers of its day not to use a BASIC written by Microsoft, instead it used a version written in house, this made converting programs written in BASIC for other machines a bit difficult. For some strange reason the BASIC was not included in the ROM but it had to be loaded by installing a cartridge into one of the two slots under the lift up trap door on top front of the machine. It had to be inserted into the slot the same way you would a video game. By the way, cartridges from the 2600 VCS do not fit in these slots. The 400 had a built in RF modulator so no special hook-ups or costly monitors were necessary, it hooked directly to any TV. 

     The Atari 400 in this exhibit is one of three working models in the museum. It was acquired through an Ebay auction and added to the museum on June 8, 2000.  It is complete in its original boxes and has all of its original documentation and accessories. Along with the purchase was an Atari 410 data recorder also in its original box.  


   System Architecture     Memory 
Microprocessor MOSTEK 6502A Standard on system board 16k
Clock speed 1.79 MHz Maximum on system board 16k
Bus type Atari proprietary   Maximum total memory 16k
Data bus width 8 - bits   Memory speed and type  
Address bus width 16 - bits   System board memory socket type Special Cartridge Slot
Interrupt levels N/A   Number of memory module sockets 1 slots
DMA channels N/A   Memory used on system board  
Standard Features   Disk Storage  
ROM size 10k   Internal disk and tape drive bays none
Optional math coprocessor no   Standard floppy drives Cassette or 5.25 floppy
Parallel port type no   Optional floppy drives: external
RS232C serial ports no   * 5 1/4 inch 160k yes
Mouse ports no   * 5 1/4 inch 1.2MB no
UART chip used N/A   * 3 1/2 inch 720k no
Maximum speed N/A   * 3 1/2 inch 1.44MB no
CMOS real time clock no   * 3 1/2 inch 2.88MB no
CMOS RAM no Hard disk controller included no
Video & Graphics Sound
Graphics Processor 'Antic'   Sound Interface device 'Pokey'
Screen size - Col x Rows 40 x 24   Sound generation 4 voices
Resolution - Colors/High 2 / 320 x 192   ADSR capable no
Resolution - Colors/Low 16 / 80 x 192      
Max colors 128 Programming Language
Sprites or Missiles 4   Built in language Atari BASIC
      Built in M L monitor no
Expansion Slots Keyboard Specs.
Total adapter slots 0   Number of keys 61 / membrane type
Number of 8/16/32 bit slots 0 / 0 / 0   Upper/lower case yes / yes
I/O 4-joystick ports   Keyboard cable length N/A
I/O 1-RF output to TV      
I/O 1-13 pin serial port      
Physical Specs. Environmental Specs.
* Height   4 1/2 inches   Operating voltage @ 60 Hz 120 VAC
* Width  13 1/2 inches   Maximum power supplied  50 Watts
* Depth  11 1/4 inches   Power supply output - volts  9 VAC
* Weight  5 pounds 3 ounces   Power supply output - amps  3.4 Amps