Sega 32X

Sega 32X
	Sega 32X add-on attached to a Mega Drive / Genesis
Specifications
Manufacturer	Sega
Type	Video game console add-on
Released	November 21, 1994 (NA), December 3, 1994 (JP), January 1995 (EU)
Discontinued	1996
Intro price	US$159 (launch)
CPU	Dual Hitachi SH-2 32-bit RISC @ 23 MHz; Zilog Z80 (via Mega Drive)
Memory	256 KB DRAM, 256 KB frame buffer, 2 × 32 KB program RAM, 256 bytes backup RAM
Storage	ROM cartridge (up to 32 Mbit)
Display	32,768 colours (15-bit), 320×224 px, hardware scaling/rotation, 50/60 Hz
Sound	Yamaha YM2612, Texas Instruments SN76489 (via Mega Drive)
Dimensions	115 mm × 210 mm × 110 mm
Weight	0.7 kg
OS / Firmware
Predecessor	Sega Mega Drive / Genesis (Model 2)
Successor	Sega Saturn (Model 1)
Codename	Mars
Model no.	MK-84000 (Japan/NA), MK-84001 (EU)

The Sega 32X is a 32-bit add-on for the Sega Mega Drive / Genesis, released in late 1994. Designed to extend the lifespan of Sega's 16-bit console, it provided enhanced graphics and processing capabilities, but saw limited commercial success due to its brief market window and competition from next-generation systems.

Architecture and Processor

The Sega 32X features a unique dual-processor architecture:

2 × Hitachi SH-2 32-bit RISC CPUs running at 23 MHz each, operating in parallel for graphics, game logic, and 3D calculations.
The add-on interfaces with the Mega Drive's Motorola 68000 (16-bit, 7.6 MHz) and Zilog Z80 (8-bit, 3.58 MHz) CPUs for backward compatibility and sound.

The SH-2 CPUs are capable of executing up to 28 MIPS combined, allowing for advanced graphical effects and 3D rendering not possible on the base Mega Drive hardware.

Memory and Storage

The 32X includes expanded memory resources:

256 KB DRAM (main memory for SH-2 CPUs)
256 KB dual frame buffer (for smooth double-buffered graphics)
2 × 32 KB program RAM (one per SH-2)
256 bytes backup RAM (for save data, battery-backed in cartridge)
ROM cartridges up to 32 Mbit (4 MB) in size

Games are loaded via dedicated 32X cartridges, which are physically larger and incompatible with standard Mega Drive-only titles.

Display and Graphics

The 32X significantly enhances the Mega Drive's video output:

Resolution: 320×224 pixels (standard), 256×224 in some modes
Colour palette: 32,768 colours (15-bit RGB), with up to 256 on-screen simultaneously
Hardware scaling and rotation for sprites and backgrounds
Dual frame buffer for flicker-free animation
Video output: Pass-through to Mega Drive A/V out (composite, RGB SCART, or RF)
Refresh rates: 50 Hz (PAL), 60 Hz (NTSC)

The 32X overlays its graphics atop the Mega Drive's video, enabling advanced effects such as texture mapping, polygonal 3D, and enhanced colour depth.

Sound Capabilities

The 32X itself does not include dedicated sound hardware, but utilises the Mega Drive's:

Yamaha YM2612 FM synthesizer (6 channels, stereo)
Texas Instruments SN76489 PSG (4 channels)
PCM playback via Mega Drive CPU

Some 32X games feature enhanced soundtracks by streaming digital audio or using the Mega Drive's sound chips in new ways, but all audio is ultimately mixed and output through the base console.

Input/Output and Expansion

The 32X connects directly to the Mega Drive / Genesis cartridge slot and A/V output, drawing power from a separate AC adapter. Key features include:

Cartridge slot (top-mounted, accepts only 32X games)
Pass-through slot for Mega Drive games (not compatible with all titles)
A/V cable links 32X to Mega Drive for video mixing
Separate power supply (9V DC, 850 mA)
Standard Mega Drive controller ports (2 × DE-9)
Compatible with Sega CD for select 32X CD-enhanced games

The unit is region-locked, with separate models for Japan, North America, and Europe.

PCB Schematics & Service Manual

**Sega 32X Main Board and Schematics**
Main Board	Schematic Diagram
Sega 32X main PCB, top view	Refer to the Sega Genesis 32X / Mega Drive 32X Service Manual

You can find the Sega 32X service manual here: Sega Genesis 32X / Mega Drive 32X Service Manual as well as the service bullitins here: Sega 32X Service Builletins

Gallery

Sega 32X add-on with Mega Drive II
Sega 32X add-on (Underside)
Sega 32X add-on (Back)
Internal view of Sega 32X PCB