Atari 260ST
The Atari 260ST is a short-case ST sold in small numbers in West Germany and parts of Scandinavia from December 1985. It is the same machine as the 520ST on the same C070243 board, and the significant point for anyone servicing one is that the "260" does not describe the amount of RAM fitted.[1]
 | |
| The 260ST. Externally it is a 520ST; the difference is inside, and it is not the RAM. | |
| Specifications | |
|---|---|
| Manufacturer | Atari Corporation |
| Type | Home computer / personal computer |
| Released | December 1985 (West Germany) |
| Discontinued | Distribution ended October 1986; production ended January 1987 |
| Intro price | DM 1,298 (December 1985, machine only) |
| CPU | Motorola MC68000 @ 8 MHz |
| Memory | 512 KB fitted (see below — the model number does not describe the RAM) |
| Storage | External 3.5-inch floppy drive (SF354 or SF314); external ACSI hard disks |
| Display | 320x200 (16 colours), 640x200 (4 colours), 640x400 mono |
| Sound | Yamaha YM-2149 PSG, three voices plus noise |
| ROM | 16 KB boot ROMs, TOS loaded from floppy disk; 192 KB ROM TOS available as a retrofit |
| Power | External linear supply, +5 V 3 A / +12 V 30 mA / -12 V 30 mA, 7-pin DIN |
| OS / Firmware | Atari TOS 1.00, loaded from disk |
| Predecessor | Atari 520ST |
| Successor | Atari 520STM |
The 256 KB machine that was never built
editAtari's product plan for 1985 had three models — the 130ST, 260ST and 520ST, with 128, 256 and 512 KB. The 130ST and 520ST were shown at the Winter CES in Las Vegas on 5 January 1985 and the 260ST was announced for June. In April 1985 the 130ST was dropped outright and the 260ST postponed, because a machine that small could not usefully run an operating system held in RAM.[1]
The machine that eventually appeared under the 260ST name, first shown at Systems '85 in Munich on 28 October 1985 and on sale that December, has 512 KB fitted. Memory prices had fallen far enough by then that building a 256 KB variant made no commercial sense.[1] A 260ST examined and measured in 2021 had 512 KB soldered to the board from the factory, showed 385 KB free when booting from ROM TOS, and 209 KB free when TOS was loaded from floppy.[2]
Atari's own engineering specification settles the point from the hardware side. The ST sizes memory through the Memory Configuration Register, and the only bank sizes that register encodes are 128 KB, 512 KB or 2 MB.[3] 256 KB is not a configuration the ST's memory controller supports at all, so a 260ST that genuinely held 256 KB could not have been configured by TOS.
The most economical reading of the name, and the one consistent with both the measurements and the register encoding, is that 260 refers to roughly the free RAM left to the user once a disk-loaded TOS is resident.
What actually differs from a 520ST
edit- No ROM TOS. The 260ST was sold without the six-chip 192 KB TOS ROM set as a cost reduction, with only the two boot ROMs fitted; TOS loads from floppy at every power-up. Atari sold a ROM TOS retrofit for DM 98.[1] Many surviving machines have had it fitted, which is why a 260ST that boots without a disk is not necessarily a fake.
- Monitor connector pin 8 is no longer tied to ground but fed from +12 V through a 1.2 kOhm resistor, which is what allows a television with a SCART socket to be driven from the monitor port.[1]
- Monitor connector pin 2 carries composite sync on this model and on the 520ST+.[1]
Everything else — case, board, chip set, connectors, external power supply — is the 520ST. See Atari ST General Maintenance for the family comparison table and the shared service data.
Not the same as the 260STD and 260STFM
editTwo other machines carried "260ST" in their names and neither reached the market. The 260STD, with 256 KB and an integral floppy drive on the left of the case, was shown at the Summer CES on 2 June 1985; the 260STFM, with the drive moved to the right and an RF modulator added, was shown in London that September. Atari dropped the "STD" suffix because of its other meaning in English, and neither model was released.[4] A machine with an internal drive is therefore not a 260ST.
Servicing
editThe 260ST is serviced exactly as a 520ST.
- Atari ST General Maintenance — disassembly, cleaning, socketed ICs, expected clock frequencies and rail figures
- Atari ST Troubleshooting Guide
- Atari ST Capacitor Replacement Guide
- Atari 520ST and 1040ST Computer Field Service Manual — Atari's own manual, hosted here
Two model-specific points:
- A 260ST still on boot ROMs will sit at the bootloader screen with no disk in the drive. That screen imitates the GEM desktop but none of its menu options do anything.[2] It is not a fault.
- External supply only. Atari specifies the brick as a linear supply delivering +5 V at 3 A, +12 V at 30 mA and -12 V at 30 mA, with a maximum input of 36 W and no adjustments.[5]
See also
editReferences
edit- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Atari 520ST, 260ST, 520ST+, 520STM, 130ST und ST Junior, atari-computermuseum.de, revised 26 June 2024. Secondary source, used here for the 1985 model plan, announcement and release dates, prices, the C070243 board number, the ROM TOS retrofit price and the monitor-connector changes. https://www.atari-computermuseum.de/520st.htm
- ↑ 2.0 2.1 Rees, Atari 260ST Story — TOS Floppy Boot Process, And How Much RAM?, ctrl.alt.rees, 7 May 2021. Bench measurements on a 260ST: 512 KB fitted at the factory, 385 KB free under ROM TOS and 209 KB free with TOS loaded from floppy, and a description of the boot ROM loader screen. https://ctrl-alt-rees.com/2021-05-07-atari-260st-story-tos-floppy-boot-process-and-how-much-ram.html
- ↑ Atari Corporation, Engineering Hardware Specification of the Atari ST Computer System, 7 January 1986, section 2.2. The Memory Configuration Register and its shadow-test sizing algorithm recognise banks of 128 KB, 512 KB or 2 MB only. Hosted here as File:Atari ST Engineering Hardware Specification.pdf.
- ↑ Atari 1040ST, atari-computermuseum.de. Secondary source, used here for the 260STD and 260STFM show appearances and for the fact that neither was released. https://www.atari-computermuseum.de/1040st.htm
- ↑ Atari Corporation, 520ST / 1040ST Computer Field Service Manual, part number CO26118-002 Rev B (3.6), January 1987, section 1, "Power Supply". Hosted here as File:Atari 520ST and 1040ST Computer Field Service Manual.pdf.