atari 520st



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Introduced  January 1985
Release Price     $799.99


        The Atari 520ST was introduced at the Winter CES in January of 1985. It is based on the Motorola 68000 16/32-bit microprocessor running at 8 MHz. The keyboard and motherboard are included in one plastic case. It was originally bundled  with an external 400K single sided 3.5 inch floppy drive, mouse and monochrome monitor for $799 and if you wanted an RGB color monitor you would pay an extra $200 dollars.

        First a little history.

        The 520ST was Jack Tramiel's response to Commodore (the company he founded) stealing the Amiga from him in a last minute bid to buy the company he was negotiating for. In January of 1984 the computer world was shocked when Jack Tramiel resigned from Commodore and sold his stock over a disagreement with the management arrangement with Irving Gould, the CEO of Commodore.

        At about the same time Warner Communications Inc., the parent company of Atari, was loosing money and wanted to sell the unprofitable subsidiary. Seeing a great opportunity Jack bought Atari and began to do what Jack did best. He immediately began to trim the fat, he cancelled all the pending 8-bit computer projects and stopped all work on the game consoles (he felt that after the video game crash of 1983 that the video game industry was dead). He closed most of Atari's factories and consolidated the ones he didn't, laying off thousands of its workers. In the end the strategy worked, a leaner more efficient Atari started to show a profit.

        With the books finally under control, Jack now had time to assess Atari's position in the computer world and its future. Realizing that the days of the 8-bit computers were getting short, he began looking for a replacement for his aging 8-bit computers that would carry the company into the next decade. 

        As luck would have it, just such a replacement was made available to him. A small silicon valley company called Amiga Inc. was experiencing financial difficulties while developing a powerful game console based on the new Motorola 68000 microprocessor codenamed 'Lorraine'. Jack wanted the Lorraine technology to create a new powerful computer to replace his 8-bit line of computers and to compete head to head with Commodore. He new that Commodore had nothing to match the Lorraine and with it he could rule the home market and ruin his old company. Unfortunately for Jack, Commodore also knew about the Lorraine and in a last minute deal out bid Jack for ownership of the Amiga Company.

        Infuriated by this, Jack immediately ordered his engineers to build him a 68000 microprocessor based computer from off the shelf components to compete with the Lorraine, and he wanted it finished before Commodore was done with the Amiga. Although the finished product was not quite as powerful as the soon to be announced Amiga computer, it wasn't far from it and Jack built it all from stock parts, no special chips. He not only beat the Amiga to market (by about 6 months!) he also did it at half the price. This was vintage Jack Tramiel.   

        The 520ST came standard with 196K of ROM and 512K of RAM and could directly access up to 16 MB of RAM without bank switching. On the left side of the case there is a 40 pin cartridge slot for plugging in ROM and game cartridges containing up to 128K. On the right side are two 9 pin D-plug ports for plugging Joysticks. The keyboard has 84 keys including a numeric keypad, cursor pad, and 10 special function keys.

        On the back of the case going from left to right is a Reset button followed by an On/Off toggle button. Next is a round port to plug a 5 pin DIN plug to supply DC power to the computer from a brick style power supply. The next two round ports are for the built in MIDI interface. Next to them is an RCA type jack for a standard TV hook-up seen on most computers of that era using an RF slide switch connector. A slide switch is provided next to allow for choosing between channels 3 or 4 depending on which channel is free in your viewing area. A 13 pin DIN port is next for connecting the 520ST to an RGB monitor. Next is an industry standard 25 pin D-plug Centronics parallel port for connecting any standard printer. Next is a standard 25 pin D-plug serial port for connecting a modem, followed by a 14 pin round DIN plug to connect an Atari serial floppy disk. Finally is an Atari hard disk port using a 19 pin D-plug.

        The 520ST has three video modes: A 640 x 400 x 2 monochrome for text base programs like word processors, a 640 x 200 x 4 color high resolution mode, and a 320 x 200 x 16 color medium resolution mode. The 520ST has a pallet of 512 colors to choose from.

        Although the video capabilities of the 520ST were good, its audio capabilities are where the computer really shines. It has a built in sound generator supplying 3 separate voices and also contains a built in MIDI interface making it possible to connect your computer to a variety of electronic instruments and state of the art sound studio equipment. All for less than $1000 dollars!

        The OS was called TOS (some say for Tramiel Operating System). The desktop was written by Digital Research Inc. and called GEM. This was a icon driven GUI similar to the MS Windows environment of that day.

        This exhibit was purchased at a local thrift shop and was added to the museum on October 30, 2000. It was purchased with three SC354 floppy drives and an Atari Mouse.


System Architecture



Microprocessor 68000 Standard on system board 512K
Clock speed 8 MHz Maximum on system board 512K
Bus type Atari proprietary Maximum total memory 16 MB
Data bus width 16-bit Memory speed and type  
Address bus width 24-bit System board memory socket type  
Interrupt levels N/A Number of memory module sockets  
DMA channels N/A Memory used on system board dynamic

Standard Features


Disk Storage

ROM size 196k Internal disk and tape drive bays none
Optional math coprocessor   Standard floppy drives external
Parallel port type centronics Optional floppy drives: yes
RS232C serial ports yes * 5 1/4 inch 160k no
Mouse ports yes * 5 1/4 inch 1.2MB no
UART chip used N/A * 3 1/2 inch 720k yes
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



Graphics Processor   Sound Interface device  
Screen size - Col x Rows 80 x 25 Sound generation 3 voices
Resolution - Colors/High 4/640 x 200 pixels ADSR capable  
Resolution - Colors/Low 16/320 x 200 pixels Built in MIDI interface yes
Max colors 512 (4096 enhanced) Programming language  
Sprites or Missiles   Built in language  
    Built in M L monitor  

Expansion Slots


Keyboard Specs.

Total adapter slots 1 Number of keys 84
Number of 8/16/32 bit slots 0/1/0 Upper/lower case yes
    Keyboard cable length N/A

Physical Specs.


Environmental Specs.

* Height 2.75 inches Operating voltage @ 60 Hz 120 VAC
* Width 18.75 inches Maximum power supplied 95 watts
* Depth 11.5 inches Power supply output - volts  
* Weight 9 pounds 7 ounces Power supply output - amps