Editing Atari ST (section)

== Design ==
[[File:Atari_520_ST_%2B_with_monochrome_monitor_SM_124.jpg|thumb|The Atari 520ST+ has 1&nbsp;MB RAM, twice that of the original model, but does not have the internal floppy drive of the 1040ST.]]

The original 520ST case design was created by Ira Velinsky, Atari's chief Industrial Designer.<ref name="case">{{cite web|title=Bold plans for new Atari|url=https://books.google.com/books?id=si4EAAAAMBAJ&q=ira+velinsky&pg=PA15|date=December 1984|work=[[InfoWorld]]|access-date=2011-08-01}}</ref> It is wedge-shaped, with bold angular lines and a series of grilles cut into the rear for airflow. The keyboard has soft tactile feedback and rhomboid-shaped function keys across the top. It is an all-in-one unit, similar to earlier home computers like the [[Commodore 64]], but with a larger keyboard with cursor keys and a numeric keypad. The original has an external floppy drive (SF354) and [[AC adapter]]. Starting with the 1040ST, the floppy drive and power supply are integrated into the base unit.

=== Ports ===
[[File:Atari520ST Interface.jpg|thumb|Atari 520ST ports]]
[[File:Atari st mouse.jpg|thumb|Atari ST mouse (2000)]]

The ports on the 520ST remained largely unchanged over its history. 

====Standard====
* [[RS-232]]c serial port ([[D-subminiature|DB25]] male, operating as basic 9-conductor DTE)
* [[Centronics printer port]] ([[D-subminiature|DB25]] female, officially compliant only with the most basic unidirectional standard with a single, "Busy" input line; unofficially offering some bidirectional capabilities)
* [[Atari joystick port]]s ([[D-subminiature|DE-9]] male) for the mouse and game controllers
* 2 [[MIDI]] ports (5-pin [[DIN connector|DIN]], "IN" and "OUT")<ref name="midi">{{cite web |title=Atari ST Interfaces & Connectors |url=http://info-coach.fr/atari/hardware/interfaces.php |website=info-coach.fr |access-date=14 August 2018}}</ref>

Because of its [[parallel communication|bi-directional]] design, the Centronics printer port can be used for joystick input, and several games used available adaptors that used the printer socket, providing two additional 9-pin joystick ports.

==== ST-specific ====
* Monitor port (custom 13-pin [[DIN connector|DIN]], 12 of the pins in a rectangular pattern, carrying signals for both RGB and monochrome monitors, monophonic audio and, in later models, composite video)
* ACSI (similar to [[SCSI]]) DMA port (custom-sized 19-pin D-sub, for hard disks and laser printers, capable of up to 2&nbsp;MB/s with efficient programming)
* Floppy port (14-pin DIN, listed as operating at 250&nbsp;kbit/s)
* ST cartridge port (double-sided 40-contact edge connector socket, for 128&nbsp;KB [[ROM cartridge]]s)

=== Monitor ===
The ST supports a [[monochrome monitor|monochrome]] or colour monitor. The colour hardware supports two resolutions: 320 × 200 pixels, with 16 of 512 colours; and 640 × 200, with 4 of 512 colours. The monochrome monitor was less expensive and has a single resolution of 640 × 400 at 71.25&nbsp;Hz. The attached monitor determines available resolutions, so each application either supports both types of monitors or only one.<ref name="byte198601">{{cite magazine | title=The Atari ST | magazine=[[Byte (magazine)|BYTE]] | volume=11 | issue=1 | date=January 1986 | url=https://archive.org/stream/byte-magazine-1986-01/1986_01_BYTE_11-01_Robotics#page/n85/mode/2up | access-date=17 April 2016 | last1=Edwards | first1=Jon R. | last2=Robinson | first2=Phillip | last3=McLaughlin | first3=Brenda | pages=84}}</ref> Most ST games require colour with productivity software favouring the monochrome. The Philips CM8833-II was a popular color monitor for the Atari ST.<ref>[https://temlib.org/AtariForumWiki/index.php/Philips_CM8833-II] temlib.org</ref><ref>[https://www.msx.org/wiki/Philips_CM_8833] msx.org</ref>

=== Floppy drive ===
{{Unreferenced section|date=December 2015}}
Atari initially used single-sided 3.5 inch floppy [[floppy disk|disk drives]] that could store up to 360&nbsp;KB. Later drives were double-sided and stored 720&nbsp;KB. Some commercial software, particularly games, shipped by default on single-sided disks, even supplying two 360&nbsp;KB floppies instead of a single double-sided one, to avoid alienating [[early adopter]]s.<ref>{{Cite web|title=XF35 Kit|url=https://www.atarimagazines.com/v8n5/XF35Kit.html|access-date=2021-09-06|website=www.atarimagazines.com}}</ref> 

Some software uses formats which allow the full disk to be read by double-sided drives but still lets single-sided drives access side A of the disk. Many magazine coverdisks (such as the first 30 issues of ''ST Format'') were designed this way, as were a few games. The music in ''[[Carrier Command]]'' and the intro sequence in ''[[Populous (video game)|Populous]]'' are not accessible to single-sided drives, for example. 

STs with double-sided drives can read disks formatted by [[MS-DOS]], but IBM PC compatibles can not read Atari disks because of differences in the layout of data on track 0.