Atari Sierra prototypes
.jpg) | |
| A wooden mock-up made for the Sierra project | |
| Specifications | |
|---|---|
| Developer | Atari Sunnyvale Research Lab |
| Manufacturer | Atari, Inc. (never produced) |
| Type | Unreleased 16/32-bit personal computer design |
| Released | Not released; design work 1983 to 1984[1] |
| CPU | Not chosen; the Motorola 68000, National Semiconductor 16032, Intel 80186 and 286, and Zilog Z8000 were considered[1] |
| Memory | — |
| Storage | — |
| Display | — |
| Sound | AMY synthesiser chip[1] |
| Graphics | Rainbow chip set (Silver and Gold)[1][2] |
| OS / Firmware | — |
| Codename | Sierra; Rainbow (graphics); Amy (sound)[1] |
Sierra was the code name for a 16/32-bit personal computer that Atari, Inc.'s Sunnyvale Research Lab (SRL) worked on from 1983 until Jack Tramiel bought the company in July 1984. It never got past block diagrams, chip designs and mock-ups: no working machine was built.[1] Its custom chips were a graphics chip set called Rainbow, made up of the Silver and Gold chips, and a sound synthesiser chip called AMY.[1] No working Sierra was ever built, so there is no machine to repair.
History
[edit | edit source]SRL, run by Alan Kay and Kristina Hooper Woolsey, began experimenting with the new 16- and 32-bit processors in the early 1980s. Steve Saunders began the Rainbow graphics design in late 1982 and worked on it through 1983 with Bob Alkire; Jack Palevich wrote a simulator and George Wang of Atari Semiconductor produced the logic design.[1] Sierra itself grew out of a conversation between Alkire and Doug Crockford. The engineers never settled on a processor, and the only parts firmly chosen were Rainbow for graphics and AMY for sound. Planned versions ranged from a home computer priced as low as $300 to business machines, student computers and low-end workstations, and the wooden mock-up dates from this stage.[1]
Atari ran other 32-bit projects in parallel, including the 68000-based Gaza workstation and "Mickey", a desktop design using the Amiga's Lorraine chip set. By early 1984 the Sierra project was expected to close, and SRL tried to license Rainbow to other companies, including Tramel Technology and AMD. After the Tramiel purchase in July 1984 most of the SRL staff were laid off; HP Labs hired about thirty SRL engineers, among them Alkire and Saunders. Only the AMY team persuaded the new owners to continue their work, and the first AMY chips were heading into production for late 1984.[1]
Rainbow graphics
[edit | edit source]Atari's November 1983 overview describes Rainbow as a "video graphics interpreter" that reads a description of the screen from memory, in the way a processor reads its instruction set. Its listed features include:[2]
- 640 × 480 pixels as the standard NTSC resolution, with coarser modes available
- Up to 256 colours on screen without help from the CPU, each held as 16 bits
- Access to one megabyte of memory over a 16-bit bus, as bus master
- A single kind of graphic object in place of the separate playfield, player and missile of ANTIC
- Dynamic memory refresh control
- Line buffers, so that CPU timing does not depend on the video clocks
- RGB or NTSC/PAL output
The overview describes 24 object processors, allowing 24 objects on a line and 11,520 on a screen.[2] Wikipedia, drawing on the Silver chip as built, gives a buffer of twelve objects and notes that this was a limit of that chip, not of the design.[1] The work is split between the two chips: Silver keeps the object data and priorities and fetches pixels from memory, acting as bus master and refreshing the DRAM, while Gold looks up the colours and generates the video timing. The split was forced by packaging: the logic was first laid out as one chip, but the only economical package at the time was the 40-pin DIP.[1]
Documentation
[edit | edit source]- Atari Sierra prototypes Documentation: Atari's Rainbow overview of 30 November 1983, hosted here.
- The rest of the Rainbow documents (the Gold chip specification of October 1983, the Silver chip specification of January 1984, an earlier overview, a state table and loose pages) are in the Internet Archive's "Atari Rainbow chipset documentation" collection, which Bob Alkire supplied in 2020.[3]
Related pages
[edit | edit source]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 Wikipedia, "Atari Sierra", revision 1355284705: SRL, the Rainbow, Silver and Gold chips, AMY, the processors considered, the mock-up, the parallel projects, the end of the project and the Silver chip's object buffer. en.wikipedia.org.
- ↑ 2.0 2.1 2.2 Atari, Inc., Rainbow overview, 30 November 1983, "Atari Company Confidential": preface (p. 1), key features (pp. 2-3), function, object processors, screen organisation and colour palette (pp. 3-4), memory and CPU communication (p. 4). Hosted as File:Atari Rainbow Overview (30 November 1983).pdf.
- ↑ Internet Archive item AtariRainbow, "Atari Rainbow chipset documentation": list of files and the note that Bob Alkire provided the documents in March 2020.