Atari SH205
| Atari SH205 | |
|---|---|
.jpg) |
|
| An SH205 (atari-computermuseum.de) | |
| Manufacturer | Atari Corporation; built by Atari Taiwan Manufacturing Corp.[1] |
| Type | 20 MB external hard disk drive |
| Release date | Fourth quarter of 1987 (SH205); late 1988 in the United States as the Megafile 20[1] |
| Discontinued | 1989 (SH205); 1991 (Megafile 20)[1] |
| Price | US$680 (Megafile 20, late 1988)[1][2] |
| Interface | Atari DMA (ACSI), two ports[3] |
| Compatible | Atari ST and TT computers[1] |
| Dimensions | 34 × 7 × 34 cm (W × H × D)[1] |
| Weight | 3.7 kg[1] |
| Predecessor | Atari SH204 |
| Successor | Atari Megafile 30 |
| Model | SH205; sold from late 1988 as the Megafile 20 |
| Storage | 21.4 MB MFM (atari-computermuseum.de)[1] |
The Atari SH205 is Atari Corporation's second 20-megabyte hard disk drive for the Atari ST, introduced in late 1987 to replace the Atari SH204 and sold from late 1988 under the name Megafile 20.[1][2] Its flat case can sit under a monitor or be stacked with a Mega ST, and it has DMA ports in and out, so it can share the bus with other drives.[1][3] Atari's later Atari Megafile 30 and Atari Megafile 60 use RLL drives.[4]
The drive contains a mains power supply. Unplug it before opening the case.
History
[edit | edit source]atari-computermuseum.de records that Atari first showed the SH205 at the Winter CES in January 1987 and put it on sale in the fourth quarter of 1987. At the Fall COMDEX in November 1987 Atari announced it as the Megafile 20, with a 40 MB Megafile 40 that was announced again at CeBIT in March 1988 but never sold. The Megafile 20 name was used in the United States from late 1988 and in Europe from the second quarter of 1989; the SH205 name was dropped in 1989 and the Megafile 20 made until 1991.[1] ST-Log reported in January 1989 that the Megafile 20, "which also goes by the name SH205", had replaced the discontinued SH204 at a list price of US$680.[2] In December 1989 ANALOG Computing wrote that Atari had ended Megafile 20 production and made the Megafile 30 its entry model.[4]
Specifications
[edit | edit source]| Item | atari-computermuseum.de[1] | ANALOG Computing, December 1989 (author's Megafile 20)[4] |
|---|---|---|
| Drive mechanism | Tandon TM262, 3.5 in | Seagate ST-225 |
| Capacity | 21.4 MB | 20 MB |
| Geometry | 615 cylinders, 2 platters, 4 heads | |
| Recording | MFM | MFM |
| Controller | Modified Adaptec 4000 controller and host adapter on one board | |
| Access time | 65 ms advertised, 86 ms measured with ICD's RATEHD.PRG | |
| Transfer rate | 625 KB/s advertised, 305 KB/s measured | |
| Power supply | 50 W | |
| Dimensions and weight | 34 × 7 × 34 cm, 3.7 kg |
The two sources name different drive mechanisms, and units may have been built with either. Read the label on the drive in your own unit. Atari's Megafile owner's manual gives the factory partitions of the SH204, SH205 and Megafile 20 as 4, 6 and 10 MB.[5]
Hardware
[edit | edit source]The controller is a single board that combines the DMA host adapter with an MFM disk controller. Atari (Japan)'s schematic C100171, drawn in March 1987 for the SH205, shows an 8085 processor (U3) running from a 64K ROM with a 2116 static RAM (U25), Adaptec's AIC-300 (U24) and AIC-010 (U33) controller chips, and an AIC-250 data separator (U29) with a 10 MHz crystal.[6] ANALOG Computing identified the same arrangement as a modified Adaptec 4000 controller and host adapter on one board, and wrote that it had "fewer bugs in its controller" than the SH204.[4] The SH204 had used a separate host adapter card and controller board.[7]
atari-computermuseum.de says the SH205, unlike the SH204, can be set to DMA addresses other than 0, so several DMA devices can share the bus.[1] Atari's Megafile owner's manual covers the SH drives as well as the Megafiles for its hard disk utilities (HDX, HINSTALL, AHDI and SHIP).[8]
The rear panel has the power switch, the mains inlet, the fan grille and two DMA ports.[3] ANALOG Computing recommended that a replacement drive draw under 25 W, and ideally under 15 W, because of the 50 W supply, and that it be a half-height drive with Seagate ST-225 mounting holes, as a full-height drive will not fit.[4]
Some later Megafile 30 units contain a controller board marked "SH205 C100169 REV.5".[9]
Repair
[edit | edit source]The SH205 shares its case with the Megafile range. The procedures on Atari Megafile General Maintenance (opening the case, head parking, the unit number switch, replacing the mechanism) and Atari Megafile Troubleshooting Guide (Atari's chart, error messages, owners' faults) apply to it; the case-opening steps there come from ANALOG Computing's article on the Megafile 20.[4] For the drive mechanism, see Hard Drive Maintenance and Repair.
ANALOG Computing found that the controller accepts any MFM drive, but that Atari's HDX recognises only 20, 30 and 60 MB mechanisms, so a larger replacement needs another formatter such as Supra's, set for the Adaptec 4000 controller.[4]
Documentation
[edit | edit source]- Atari SH205 Documentation: the first sheet of the SH205 controller schematic, C100171.
- Atari Megafile Documentation: the Megafile owner's manual, which covers the SH drives' utilities and default partitions.
Gallery
[edit | edit source]-
Rear of an SH205 (atari-computermuseum.de)
.jpg)
Related pages
[edit | edit source]- Atari SH205 Documentation
- Atari SH204
- Atari Megafile 30, Atari Megafile 60
- Atari Megafile General Maintenance, Atari Megafile Troubleshooting Guide
- Hard Drive Maintenance and Repair
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 "Atari SH205 / MEGAFILE 20 / MEGAFILE 40 Hard Disk Drive", in "Atari ST-Peripheriegeräte", atari-computermuseum.de, https://www.atari-computermuseum.de/st_peri.htm#sh205. Secondary source for the maker, factory code, showings, sales dates, end of production, price, drive mechanism and geometry, case, size, weight and DMA addressing.
- ↑ 2.0 2.1 2.2 "ST News: Megafile 20", ST-Log issue 27, January 1989, p. 9. https://www.atarimagazines.com/st-log/issue27/109_3_ST_NEWS_MEGAFILE_20.php
- ↑ 3.0 3.1 3.2 Photograph of the rear of an SH205, atari-computermuseum.de. File:Atari SH205 rear panel (Atari Computermuseum).jpg.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Gregg Anderson, "Massaging Your MegaFile", ANALOG Computing issue 79, December 1989, p. 114: the Megafile 20's drive, controller, power supply and performance, end of production, drive replacement and formatting. https://www.atarimagazines.com/analog/issue79/megafile.php
- ↑ Atari Corporation, MEGAFILE Hard Disk Drive Owner's Manual, C300459-001 Rev. B, 1988, chapter 2, Default Partition Sizes Table, p. 11 (PDF p. 14). File:Atari Megafile Owner's Manual C300459-001 Rev B.pdf.
- ↑ Atari (Japan) Corporation, Schematic Diagram (SH205), drawing C100171, sheet 1 of 2, drawn 5 March 1987. File:Atari SH205 Schematic C100171 sheet 1.pdf.
- ↑ See Atari SH204, section Hardware.
- ↑ MEGAFILE Hard Disk Drive Owner's Manual, introduction and chapter 1, The Atari Hard Disk Utilities (PDF pp. 5 and 11-12).
- ↑ See Atari Megafile 30, section Controller board, citing an AtariAge forum thread of August 2022.