Editing Atari ST (section)

== Technical specifications ==
All STs are made up of both custom and commercial chips.
* Custom chips:
** ST Shifter "Video shift register chip": Enables bitmap graphics using 32&nbsp;KB of contiguous memory for all resolutions. Screen address has to be a multiple of 256.
** ST GLU "Generalized Logic Unit": Control logic for the system used to connect the ST's chips. Not part of the data path, but needed to bridge chips with each other.
** ST MMU "Memory Management Unit": Provides signals needed for CPU/blitter/DMA and Shifter to access dynamic RAM. Even memory accesses are given to CPU/blitter/DMA while odd cycles are reserved for DRAM refresh or used by Shifter for displaying contents of the frame buffer.
** ST DMA "[[Direct Memory Access]]": Used for floppy and hard drive data transfers. Can directly access main memory in the ST.
* Support chips:
** MC6850P ACIA "Asynchronous Common Interface Adapter": Enables the ST to directly communicate with MIDI devices and keyboard (two chips used). {{nowrap|31.250&nbsp;kbit/s}} for [[MIDI]], {{nowrap|7812.5 bit/s}} for keyboard.
** MC68901 MFP "Multi Function Peripheral": Used for interrupt generation/control, serial and misc. control input signals. Atari TT030 has two ''MFP'' chips.
** [[Western Digital FD1771|WD-1772-PH]] "Western Digital Floppy Disk Controller": Floppy controller chip.
** [[General Instrument AY-3-8910|YM2149F PSG]] "[[Programmable Sound Generator]]": Provides three-voice sound synthesis, also used for floppy signalling, serial control output and printer parallel port.
** HD6301V1 "Hitachi keyboard processor": Used for keyboard scanning and mouse/joystick ports.

=== ST/ST<sup>F</sup>/ST<sup>M</sup>/ST<sup>FM</sup> ===
As originally released in the 520ST:

* CPU: [[Motorola 68000]] 16-/32-bit CPU<ref "16/32">{{cite book | title = M68000 Family Programmer's Reference Manual | publisher = Motorola | year = 1992 | pages = 1 | isbn = 0-13-723289-6 }}</ref> @ 8&nbsp;[[Megahertz|MHz]]. 16-bit data/32-bit internal/24-bit address.
* RAM: 512&nbsp;KB or 1&nbsp;[[Megabyte|MB]]
* Display modes (60&nbsp;Hz NTSC, 50&nbsp;Hz PAL, 71.2&nbsp;Hz monochrome):
** Low resolution: 320 × 200 (16 color), palette of 512 colors
** Medium resolution: 640 × 200 (4 color), palette of 512 colors
** High resolution: 640 × 400, monochrome
* Sound: [[General Instruments AY-3-8912|Yamaha YM2149]] 3-voice square wave plus 1-voice white noise mono [[Programmable Sound Generator]]
* Drive: Single-sided 3{{frac|1|2}}" [[floppy disk]] drive, 360&nbsp;KB capacity when formatted to standard 9 sector, 80 track layout.
* Ports: TV out (on ST-M and ST-FM models, NTSC or PAL standard RF-modulated), [[MIDI]] in/out (with 'out-thru'), [[RS-232]] serial, [[Centronics]] parallel (printer), monitor ([[RGB]] or Composite Video color and mono, 13-pin [[DIN connector|DIN]]), extra disk drive port (14-pin [[DIN connector|DIN]]), [[Direct memory access|DMA]] port (ACSI port, Atari Computer System Interface) for [[hard disk]]s and Atari Laser Printer (sharing RAM with computer system), joystick and mouse ports (9-pin MSX standard)
* [[Operating System]]: [[Atari TOS|TOS]] v1.00 with [[Graphics Environment Manager]] (GEM)

Very early machines have the OS on a floppy disk before a final version was burned into ROM. This version of TOS was bootstrapped from a small core [[boot ROM]].

In 1986, most production models became ST<sup>F</sup>s, with an integrated single- (520STF) or double-sided (1040STF) double density floppy disk drive built-in, but no other changes. Also in 1986, the ''520ST<sup>M</sup>'' (or ''520STM'') added an [[RF modulator]] for allowing the low and medium resolution color modes when connected to a TV. Later ''F'' and ''FM'' models of the 520 had a built-in [[double-sided disk]] drive instead of a single-sided one.

=== ST<sup>E</sup> ===
As originally released in the 520ST<sup>E</sup>/1040ST<sup>E</sup>:

* All of the features of the 520STFM/1040STFM
* Extended palette of 4,096 available colors to choose from
* [[Blitter]] chip (stylized as BLiTTER) to copy/fill/clear large data blocks with a max write rate of 4&nbsp;Mbytes/s
* Hardware support for horizontal and vertical fine scrolling and split screen (using the Shifter video chip){{Citation needed|date=September 2021}}
* DMA [[sound chip]] with 2-channels stereo 8-bit [[pulse-code modulation|PCM]] sound at 6.25/12.5/25/50&nbsp;kHz and stereo RCA audio-out jacks (using enhancements to the Shifter video chip to support audio shifting)
* National LMC 1992 audio controller chip, allowing adjustable left/right/master volume and bass and treble EQ via a [[Serial Peripheral Interface Bus#Microwire|Microwire]] interface
* Memory: 30-pin [[SIMM]] memory slots ([[SIPP memory|SIPP]] packages in earliest versions) allowing upgrades up to 4&nbsp;MB Allowable memory sizes including only 0.5, 1.0, 2.0, 2.5 and 4.0&nbsp;MB due to configuration restraints (however, 2.5&nbsp;MB is not officially supported and has compatibility problems). Later third-party upgrade kits allow a maximum of 14&nbsp;MB w/Magnum-ST, bypassing the stock [[Memory management unit|MMU]] with a replacement unit and the additional chips on a separate board fitting over it.
* Ability to synchronize the video timings with an external device so that a video [[Genlock]] device can be used without having to make any modifications to computer's hardware
* Analogue joypad ports (2), with support for devices such as paddles and light pens in addition to joysticks/joypads. The [[Atari Jaguar]] joypads and Power Pad joypads (gray version of Jaguar joypads marketed for the ST<sup>E</sup> and [[Atari Falcon|Falcon]]) can be used without an adapter. Two standard Atari-style digital joysticks could be plugged into each analogue port with an adapter.
* [[Atari TOS|TOS]] 1.06 (also known as TOS 1.6) or TOS 1.62 (which fixed some major backwards-compatibility bugs in TOS 1.6) in two socketed 128&nbsp;KB ROM chips.
* Socketed [[Plastic leaded chip carrier|PLCC]] [[Motorola 68000|68000]] [[Central processing unit|CPU]]