Atari 520ST+
 | |
| An Atari 520ST+ with a floppy drive, SM124 monochrome monitor and mouse | |
| Specifications | |
|---|---|
| Manufacturer | Atari Corporation |
| Type | Home computer |
| Released | Shown 28 October 1985 (Systems '85, Munich) |
| Discontinued | 1988 |
| Intro price | DM 2,998 with monochrome monitor (October 1985); DM 2,698 (March 1986) |
| CPU | Motorola MC68000 at 8 MHz |
| Memory | 1 MB, thirty-two 256 kbit × 1 DRAMs in two banks |
| Storage | External 3.5-inch floppy drive (SF354 or SF314); external floppy (14-pin DIN) and hard disk (DB-19) ports |
| Display | 320 × 200 (16 colours), 640 × 200 (4 colours), 640 × 400 monochrome |
| Sound | Yamaha YM2149 programmable sound generator, three channels |
| ROM | 192 KB ROM TOS from February 1986; earlier machines have the 16 KB boot ROMs and load TOS from disk |
| Power | External linear supply: +5 V 3 A, +12 V 30 mA, −12 V 30 mA, 7-pin DIN |
| OS / Firmware | TOS 1.00 |
| Predecessor | Atari 520ST |
| Successor | Atari 520STM |
The Atari 520ST+ is a short-case Atari 520ST with both banks of RAM fitted, giving 1 MB. Atari showed it with the 260ST at Systems '85 in Munich on 28 October 1985 and sold it at the price the 512 KB 520ST had carried, which upset some existing ST owners; memory prices were falling fast at the time.[1] The 520ST+ and 260ST were meant to replace the 520ST, whose production ended in April 1986.[1]
The 520ST+ uses the same C070243 board, case and external power supply as the 520ST and 260ST, and has no internal drive.[1] Atari's schematic for the board is drawing C070231.[2] From February 1986 the 520ST and 520ST+ shipped with TOS in ROM in place of the two boot ROMs.[1] In West Germany the 520STM replaced the 520ST+ and 260ST from October 1986, and the 520ST+ was withdrawn in 1988.[1]
The 520ST+ came before the 1040ST. Atari introduced the 1040ST at the Winter Consumer Electronics Show in January 1986, and it went on sale in March 1986, so the 520ST+ was the first ST sold with 1 MB.[3][4]
Memory
[edit | edit source]The ST's RAM is built from 256 kbit × 1 DRAMs. A 512 KB machine carries 16 of them in one bank; a 1 MB machine carries a second bank of 16, 32 in total.[5] The 520ST+ is a 520ST with that second bank fitted.
TOS sizes each bank at power-up with a shadow test, writing a pattern and reading it back at addresses that distinguish 128 KB, 512 KB and 2 MB banks, and then programs the memory controller's configuration register. If bank 1 fails all three tests, Atari's specification treats it as not fitted; only a failure in bank 0 stops the machine.[6] A 520ST+ that reports 512 KB therefore points at the second bank of DRAMs or the lines that drive it, and the rest of the machine is probably working.
The German Atari museum notes that the 260ST and 520ST+ carry composite sync on monitor pin 2.[1] In other respects the hardware is the 520ST's; see Atari 520ST for the chip set, ports and pinouts, and Atari ST General Maintenance for the family comparison.
Power supply
[edit | edit source]The external supply is a linear unit with regulated +5 V, +12 V and −12 V and no adjustments. Atari rates it at 3 A on +5 V and 30 mA on each 12 V rail, with 36 W maximum input. Atari gives typical demand in a 520ST as 1.5 A at 5 V, and 3 mA on each 12 V rail with RS-232 idle, rising to 19 mA on +12 V and 18 mA on −12 V when it is active.[5]
Servicing
[edit | edit source]- Atari ST General Maintenance
- Atari ST Troubleshooting Guide
- Atari ST Capacitor Replacement Guide
- Atari 520ST and 1040ST Computer Field Service Manual, Atari's service manual
- Atari 520ST/260ST schematic C070231
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "Atari 520ST, 260ST, 520ST+, 520STM, 130ST und ST Junior", atari-computermuseum.de (in German), revised 26 June 2024. Secondary source for the 520ST+ showing at Systems '85 on 28 October 1985, its prices and the owners' reaction, the C070243 board, the February 1986 change to ROM TOS, the replacement by the 520STM in West Germany, the 1988 withdrawal and the pin 2 composite sync.
- ↑ Atari (Japan) Corporation, Schematic Diagram (520ST/260ST), drawing C070231, three sheets, revision M, April 1986. Hosted on this wiki: File:Atari 520ST Schematic C070231.pdf.
- ↑ "A Turning Point for Atari? Report from the Winter Consumer Electronics Show", Compute! issue 71, April 1986, p. 30. Source for the introduction of the 1040ST at the January 1986 show.
- ↑ "Atari 1040ST", atari-computermuseum.de (in German). Secondary source for the 1040STF going on sale in March 1986.
- ↑ 5.0 5.1 Atari Corporation, 520ST/1040ST Computer Field Service Manual, part number C026118-002 Rev B (3.6), January 1987: section 1, "Power Supply" (p. 1.6), for the external supply rating and in-system demand, and section 2, "Main Memory" (p. 2.3), for the DRAM organisation. Hosted on this wiki: Atari 520ST and 1040ST Computer Field Service Manual (PDF).
- ↑ Atari Corporation, Engineering Hardware Specification of the Atari ST Computer System, 7 January 1986, section 2.2, "Memory Configuration", with the shadow-test sizing algorithm. Hosted on this wiki: Atari ST Engineering Hardware Specification (PDF).