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ATARI 520ST+

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ATARI 520ST+ logo (8 KBytes)

ATARI 520ST⁺

ATARI 520ST+ (57 KBytes)

ATARI 520ST⁺ with STM1 mouse
(picture copyright by M.A.Grundke)

Specifications

Name ATARI 520ST⁺

Made by ATARI Corp.
Sunnyvale, California

Released
Fall 1985 on a German trade fair
first ST-prototypes were shown on CES 1985 (i.e. a 130ST with 128KB RAM)
first 520ST were sold in Summer 1985

Serial-No. A1 4004726

Board-info
ATARI® C070243 REV.H
also see the board overview

CPU Motorola MC68000
C025915-38A 'GLUE'
although having 16 bit data/ 24 bit address bus, the MC68000 internally processes 32 bits, thus the 'ST' (meaning 'sixteen thirtytwo')
GLUE is the ST-architecture's 'Control logic' and coordinates all of its components

Speed 8 MHz

RAM C025912-38 MMU
1024 KBytes:
16 pcs. Samsung KM41256 (256Kx1)
16 pcs. NEC D41256C (256Kx1)
expandable to 4096 KBytes, which is also MMU-limit
since the 520ST-mainboard can only take 16 256Kx1 RAMs, ATARI's choice for the 520ST⁺ was a 'pick-a-back solution': a daughterboard with 16 additional RAMs was put into the Shifter-socket; additional signals were taken from the MMU via PLCC-adaptor. On the earlier REV.C boards, by the way, the additional RAMs were simply soldered onto the existing ones

ROM/ Native OS PAL TOS 1.0 ('The Operating System')
in 6x 32 KBytes ROM
up to 320 KBytes ROM via external cartridge
this early TOS comes on six 256Kx1 chips - even earlier machines only had a 16K Boot-ROM, and startet TOS from disk
TOS is also known as 'Tramiel Operating System', after Jack Tramiel (ATARI's boss these days). It's based on CP/M-68k, a MC68000 conversion of Gary Kildall's CP/M ('Control Program for Microcomputers'), adding a graphical user interface (GUI) similar to that of the Macintosh. Since both CP/M and GEM were products of Kildall's company Digital Research, Incorporated, it was easy to merge them and a clever decision
the last official TOS version was 4.04, used in the ATARI FALCON 030

Keyboard/ Layout Motorola SC400020P (C070122-002, keyboard control)
95 keys/ german (QWERTZ) layout

Graphics C025914-38 'Shifter' (Video Shift Register Chip)
Resolutions:
320x200 ('LowRes', requires RGB-monitor)
640x200 ('MedRes', requires RGB-monitor)
640x400 ('HighRes', requires monochrome monitor)
Colors:
16 at 320x200 from 512 color palette
4 at 640x200 from 512 color palette
monochrome at 640x400
all 512 in LowRes with tricks possible

Text: 80x25 characters (although no 'real' text-mode)
PAL version; PAL or NTSC are detected via interrupt by the 68901. However, this is only interesting for LowRes and MedRes modes (50/ 60 Hz) - in HighRes, refresh is always 72 Hz
Upon operation, the ST's graphic subsystem takes 32 KBytes of RAM to utilize as 'BitMap video display memory'
Later machines (from 1040ST^FM on) used a 'BLiTTER' to speed up filling-operations (mainly to speed up GEM)

In the 520ST⁺, Shifter resides on the RAM-daughterboard

Sound Yamaha YM2149F
'Programmable Sound Generator'
3 independent voices, programmable volume; dynamic envelope shaping; wave shaping; programmable attack, decay, sustain, release; frequency range: 30 Hz to 125 KHz
built-in D/A converters
special: two MIDI IN and MIDI OUT ports controlled by the ACIAs

Media WD 1772-PH floppy-controller
C025913-38 DMA for floppy- and harddisk-access
up to 2 external drives using 3.5" disks with
360 KBytes/ disk (single-sided) or
720 KBytes/ disk (double-sided)
5.25" diskdrives, 360 KByte/ disk for PC-DD-compatibility
external harddisks at various sizes (e.g. ATARI Megafile)

Input/ Output 2x Motorola MC6850P ACIA ('Asynchchronous Communications Interface Adaptor')
Motorola MC1488 + MC1489 (RS232)
Motorola SC87898P 'Multi-Function Peripheral'
Motorola SC400020P (C070122-002, 1 MHz, for basic-I/O and clock)
2x 9 pin SUB-D joystick/ mouse connectors
40 pin female edge conn. expansion bus

2x 5 pin round-DIN MIDI IN and OUT (31.25 KBaud)
13 pin round-DIN monitor-out (RGB-type)
25 pin parallel SUB-D
25 pin serial SUB-D (RS232C compliant, 19.2 KBaud max)
14 pin round-DIN external diskdrive-conn.
19 pin SUB-D for external harddisks
7 pin round conn. for external power supply
has a reset-button

Miscellaneous
The 520ST⁺ was direct heir to the 520ST, the first ST-model, and introduced in the same year, 1985, on a German fair. It was based on the same board, but came with double the amount of RAM for the same price. Sounds easier than it actually was, since the 520ST mainboard wasn't designed to take more than 512 KBytes - ATARI had to do some patchwork to the boards (see RAM above). However, when the 1040ST was introduced later, it was designed to take up to 4 MBytes RAM from the beginning. Also notable is that some 520ST were not upgraded to 520ST⁺ (i.e. 1 MByte), but instead were rebadged and sold as 260ST

The ST-series soon became very popular. Because of its comfortable, 'Mac-like' user-interface GEM, many people called it the 'Jackintosh' (refering to ATARI-boss Jack Tramiel). It was interesting especially for musicians because of its MIDI IN/OUT ports, and, generally, because of its low price and ergonomic 72 Hz HighRes mode

ATARI tried to rival the Amiga with it, but failed. The Amiga was better suited for games and graphics, and so it sold more often than the ST-series did. When ATARI realized that and released the ST^E-series ('enhanced ST') in 1989, it was far too late. Since there wasn't much software using the new machines' capabilities (4096 color palette, stereo PCM-sound), they didn't sell. The ST^E-series consisted of 520ST^E, 1040ST^E, 4160ST^E and Mega ST^E, and also had other advantages like better RAM-expandibility (SIP/ SIMM)
There was also an interesting ST^E-prototype: the 1040ST^E+ came with an additional onboard 80286

TOS 1.00 german screenshot (10 KBytes)

Screenshot of the German PAL TOS 1.00 from 1985 (by the way, one of the first ROM TOSes). What you see here is the ST's high resolution (640x400 monochrome), which the SM124 was able to display with 72 Hz refresh, making the ST the probably most ergonomic machine of its time! If you wanted color, however, you needed a color monitor like the SC1224 which could only display the ST's low- and mid-res modes (320x200, 640x200)

All trademarks mentioned on these pages belong to their respective owners (if they still exist). All other content, including pictures is (C) M.A.Grundke (aka Sothius), unless otherwise noted. Unauthorized copying or usage of that content, without former permission from M.A.Grundke or the rightful copyright-holder, is prohibited

Sothius' Home - Museum - ATARI - ATARI 520ST+ - additional pictures

Name	ATARI 520ST⁺
Made by	ATARI Corp. Sunnyvale, California
Released	Fall 1985 on a German trade fair first ST-prototypes were shown on CES 1985 (i.e. a 130ST with 128KB RAM) first 520ST were sold in Summer 1985
Serial-No.	A1 4004726
Board-info	ATARI® C070243 REV.H also see the board overview
CPU	Motorola MC68000 C025915-38A 'GLUE' although having 16 bit data/ 24 bit address bus, the MC68000 internally processes 32 bits, thus the 'ST' (meaning 'sixteen thirtytwo') GLUE is the ST-architecture's 'Control logic' and coordinates all of its components
Speed	8 MHz
RAM	C025912-38 MMU 1024 KBytes: 16 pcs. Samsung KM41256 (256Kx1) 16 pcs. NEC D41256C (256Kx1) expandable to 4096 KBytes, which is also MMU-limit since the 520ST-mainboard can only take 16 256Kx1 RAMs, ATARI's choice for the 520ST⁺ was a 'pick-a-back solution': a daughterboard with 16 additional RAMs was put into the Shifter-socket; additional signals were taken from the MMU via PLCC-adaptor. On the earlier REV.C boards, by the way, the additional RAMs were simply soldered onto the existing ones
ROM/ Native OS	PAL TOS 1.0 ('The Operating System') in 6x 32 KBytes ROM up to 320 KBytes ROM via external cartridge this early TOS comes on six 256Kx1 chips - even earlier machines only had a 16K Boot-ROM, and startet TOS from disk TOS is also known as 'Tramiel Operating System', after Jack Tramiel (ATARI's boss these days). It's based on CP/M-68k, a MC68000 conversion of Gary Kildall's CP/M ('Control Program for Microcomputers'), adding a graphical user interface (GUI) similar to that of the Macintosh. Since both CP/M and GEM were products of Kildall's company Digital Research, Incorporated, it was easy to merge them and a clever decision the last official TOS version was 4.04, used in the ATARI FALCON 030
Keyboard/ Layout	Motorola SC400020P (C070122-002, keyboard control) 95 keys/ german (QWERTZ) layout
Graphics	C025914-38 'Shifter' (Video Shift Register Chip) Resolutions: 320x200 ('LowRes', requires RGB-monitor) 640x200 ('MedRes', requires RGB-monitor) 640x400 ('HighRes', requires monochrome monitor) Colors: 16 at 320x200 from 512 color palette 4 at 640x200 from 512 color palette monochrome at 640x400 all 512 in LowRes with tricks possible Text: 80x25 characters (although no 'real' text-mode) PAL version; PAL or NTSC are detected via interrupt by the 68901. However, this is only interesting for LowRes and MedRes modes (50/ 60 Hz) - in HighRes, refresh is always 72 Hz Upon operation, the ST's graphic subsystem takes 32 KBytes of RAM to utilize as 'BitMap video display memory' Later machines (from 1040ST^FM on) used a 'BLiTTER' to speed up filling-operations (mainly to speed up GEM) In the 520ST⁺, Shifter resides on the RAM-daughterboard
Sound	Yamaha YM2149F 'Programmable Sound Generator' 3 independent voices, programmable volume; dynamic envelope shaping; wave shaping; programmable attack, decay, sustain, release; frequency range: 30 Hz to 125 KHz built-in D/A converters special: two MIDI IN and MIDI OUT ports controlled by the ACIAs
Media	WD 1772-PH floppy-controller C025913-38 DMA for floppy- and harddisk-access up to 2 external drives using 3.5" disks with 360 KBytes/ disk (single-sided) or 720 KBytes/ disk (double-sided) 5.25" diskdrives, 360 KByte/ disk for PC-DD-compatibility external harddisks at various sizes (e.g. ATARI Megafile)
Input/ Output	2x Motorola MC6850P ACIA ('Asynchchronous Communications Interface Adaptor') Motorola MC1488 + MC1489 (RS232) Motorola SC87898P 'Multi-Function Peripheral' Motorola SC400020P (C070122-002, 1 MHz, for basic-I/O and clock) 2x 9 pin SUB-D joystick/ mouse connectors 40 pin female edge conn. expansion bus 2x 5 pin round-DIN MIDI IN and OUT (31.25 KBaud) 13 pin round-DIN monitor-out (RGB-type) 25 pin parallel SUB-D 25 pin serial SUB-D (RS232C compliant, 19.2 KBaud max) 14 pin round-DIN external diskdrive-conn. 19 pin SUB-D for external harddisks 7 pin round conn. for external power supply has a reset-button
Miscellaneous	The 520ST⁺ was direct heir to the 520ST, the first ST-model, and introduced in the same year, 1985, on a German fair. It was based on the same board, but came with double the amount of RAM for the same price. Sounds easier than it actually was, since the 520ST mainboard wasn't designed to take more than 512 KBytes - ATARI had to do some patchwork to the boards (see RAM above). However, when the 1040ST was introduced later, it was designed to take up to 4 MBytes RAM from the beginning. Also notable is that some 520ST were not upgraded to 520ST⁺ (i.e. 1 MByte), but instead were rebadged and sold as 260ST The ST-series soon became very popular. Because of its comfortable, 'Mac-like' user-interface GEM, many people called it the 'Jackintosh' (refering to ATARI-boss Jack Tramiel). It was interesting especially for musicians because of its MIDI IN/OUT ports, and, generally, because of its low price and ergonomic 72 Hz HighRes mode ATARI tried to rival the Amiga with it, but failed. The Amiga was better suited for games and graphics, and so it sold more often than the ST-series did. When ATARI realized that and released the ST^E-series ('enhanced ST') in 1989, it was far too late. Since there wasn't much software using the new machines' capabilities (4096 color palette, stereo PCM-sound), they didn't sell. The ST^E-series consisted of 520ST^E, 1040ST^E, 4160ST^E and Mega ST^E, and also had other advantages like better RAM-expandibility (SIP/ SIMM) There was also an interesting ST^E-prototype: the 1040ST^E+ came with an additional onboard 80286