Sega Saturn (Model 2)
The Sega Saturn (Model 2) is a 32-bit fifth-generation home video game console developed by Sega. Released in Japan in late 1994 and internationally in 1995, the Saturn is renowned for its advanced dual-CPU architecture and powerful 2D and 3D graphics capabilities, making it a favourite among retro gaming enthusiasts.
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| Sega Saturn Model 2 | |
| Specifications | |
|---|---|
| Manufacturer | Sega |
| Type | Home video game console |
| Released | November 22, 1994 (Japan); May 11, 1995 (North America); July 8, 1995 (Europe) |
| Discontinued | 2000 (Japan); 1998 (North America/Europe) |
| Intro price | JP¥44,800 (launch); US$399 (launch) |
| CPU | Dual Hitachi SH-2 32-bit RISC @ 28.6 MHz |
| Memory | 2 MB RAM, 1.54 MB VRAM, 512 KB sound RAM, 4 MB CD buffer RAM |
| Storage | CD-ROM (2× speed), optional backup RAM cartridge |
| Display | 320×224 to 704×480, 16.77 million colours (24-bit, 32,768 on screen) |
| Sound | Yamaha YMF292-F (SCSP): 32-channel PCM/ADPCM, 8–44.1 kHz, 16-bit stereo |
| Dimensions | 260 mm × 230 mm × 83 mm |
| Weight | 2.0 kg |
| OS / Firmware | Sega proprietary BIOS |
| Predecessor | Sega Mega Drive / Genesis (Model 1) |
| Successor | Dreamcast |
| Codename | Saturn |
| Model no. | HST-3220 (Model 2) |
Architecture and Processor
The Sega Saturn is powered by a complex, parallel-processing architecture designed to excel at both 2D sprite manipulation and 3D polygonal graphics. Its main processing components include:
- Dual Hitachi SH-2 32-bit RISC CPUs running at 28.6 MHz, operating in parallel for increased performance.
- Hitachi SH-1 as the CD-ROM controller.
- Two custom video display processors:
- VDP1 – Handles sprites and polygons (2D/3D graphics).
- VDP2 – Manages backgrounds, scrolling, and effects.
- Additional support chips for sound, DMA, and I/O.
This architecture allowed for advanced graphical effects, but also posed programming challenges due to its complexity.
Memory and Storage
The Saturn Model 2 features a diverse memory map optimised for graphics and sound:
- 2 MB main RAM
- 1.54 MB VRAM (split between VDP1 and VDP2)
- 512 KB sound RAM
- 4 MB CD-ROM buffer RAM
- 32 KB backup RAM (internal), expandable via optional cartridge
Storage is provided by a 2× speed CD-ROM drive, supporting up to 640 MB per disc. Game saves are stored in internal backup RAM or on external RAM cartridges.
Display and Graphics
The Saturn's graphics subsystem is built around its dual VDPs:
- Resolution: 320×224 to 704×480 pixels (interlaced and non-interlaced modes)
- Colour palette: 16.77 million (24-bit), with up to 32,768 colours displayed simultaneously
- VDP1: Renders sprites, polygons, scaling, rotation, and texture mapping
- VDP2: Handles up to five scrolling background planes, transparency, and special effects
Hardware support for both 2D and 3D graphics made the Saturn especially strong for arcade-style and sprite-based games.
Sound Capabilities
Audio on the Saturn is powered by the Yamaha YMF292-F (SCSP) sound processor:
- 32 sound channels supporting PCM and ADPCM playback
- Sampling rates from 8 kHz to 44.1 kHz, 16-bit stereo output
- Integrated DSP for effects such as reverb and modulation
- Additional Motorola 68EC000 CPU (11.3 MHz) for sound control
This robust sound system enabled high-quality music and effects, including streaming audio from CD.
Input/Output and Expansion
The Saturn Model 2 offers a wide range of connectivity and expansion options:
- Controller ports: 2 × proprietary 9-pin connectors (supporting digital and analogue pads, multitap)
- AV output: Composite video, S-Video, RGB SCART (PAL/JP), stereo audio
- Serial port: For link cable multiplayer
- Cartridge slot: For backup RAM, ROM cartridges, and RAM expansion (up to 4 MB for certain games)
- Communication connector: For modem or network peripherals (Japan only)
- Power: Internal PSU (100–240 V, region dependent)
PCB Schematics & Service Manual
The Model 2 Saturn features a revised mainboard with integrated components and simplified circuitry compared to the original model. Service documentation and schematics are available for maintenance and repair.
| Mainboard (Model 2) | Mainboard Schematic |
|---|---|
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- For detailed board layouts and service procedures, refer to the Sega Saturn Service Manual.
Gallery
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Sega Saturn Model 2 -
Model 2 mainboard -
Power supply unit -
Standard Saturn controller (Model 2)
