Sega Saturn (Model 2)

Sega Saturn (Model 2)
	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)

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.

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.