Sega 32X/Technical Specifications

This page details the technical specifications of the Sega 32X.

Technical Specifications[]

Main CPU: 2x Hitachi SH-2 (SH7095) 32-bit RISC processors
- Clock speed: 23.01136 MHz (NTSC), 22.801467 MHz (PAL)
- Clock cycles: 46.022721 MHz (NTSC, 23.01136 MHz per SH-2), 45.602934 MHz (PAL, 22.801467 MHz per SH-2)
- 2x CPU cores: 32‑bit RISC instructions/registers, up to 4 instructions/cycle (2 instructions/cycle per SH-2), 1.3 MIPS per MHz, 59.829537 MIPS (NTSC, 29.914768 MIPS per SH-2), 59.283814 MIPS (PAL, 29.641907 MIPS per SH-2)
- 4x internal fixed‑point math processors: 2x MULT multiplier DSP, 2x DIVU division units, parallel processing
- 2x MULT multiplier DSP: 46.022721 MOPS (NTSC, 23.01136 MOPS per SH-2), 45.602934 MOPS (PAL, 22.801467 MOPS per SH-2)
- 2x DIVU division units: 16/32/64-bit division, 1,180,069 divides/sec
- 2x DMA units: 2x DMAC (Direct Memory Access Controller), parallel processing
- Bus width: 64‑bit (2× 32‑bit) internal, 32‑bit external
CPU co-processors: Overlay/Underlay processors
- Genesis CPU:
  - Motorola M68000 — 7.670453 MHz (NTSC), 7.600489 MHz (PAL), 16/32-bit instructions, 32-bit internal data bus, 16-bit external data bus, 1.342329 MIPS (NTSC), 1.330085 MIPS (PAL)
  - Zilog Z80 — 3.579545 MHz (NTSC), 3.546894 MHz (PAL), 8/16-bit instructions, 8-bit data bus, 0.519034 MIPS (NTSC), 0.514299 MIPS (PAL)
- Sega CD CPU: Motorola M68000 — 12.5 MHz, 2.1875 MIPS

Graphics
- 32X graphics chip: Sega 32X VDP (Sega Custom LSI) @ 23.01136 MHz (NTSC), 22.801467 MHz (PAL)
- Data bus width: 32-bit (16-bit per framebuffer)
- Word length: 16-bit
- Features: 3D polygon graphics, Gouraud shading, texture mapping, more sprites, quicker animation
- Color palette: 32,768 colors
- Double-buffered framebuffer with three modes:
  - 8bpp "packed pixel" mode: 256 simultaneous colors on screen; each pixel is an index into CRAM (can use full screen)
  - 16bpp "run length" mode: 256 simultaneous colors on screen; each pixel is both a number of pixels to display and the index of CRAM (limits screen size)
  - 16bpp "direct color" mode: 32,768 simultaneous colors on screen; each pixel is the color value (limits screen size)
- VRAM: 256 KB, split into two 128 KB segments for each framebuffer. A priority system allows partial overlaying/underlaying of Mega Drive/Mega-CD graphics.
  - Sprites, polygons and textures accessed from 256 KB main SDRAM and 4–8 MB ROM cartridge.
- Resolutions: 320×224, 320×240, 320×204 (direct color), 320×408 (8bpp)
  - Overscan: 450×262 (NTSC), 450×313 (PAL)
- Refresh rate: 60 Hz (NTSC), 50 Hz (PAL)
  - Maximum frame rate: 60 FPS (NTSC), 50 FPS (PAL)
- Framebuffer bandwidth: 72.727272 MB/s (36.363636 MB/s per framebuffer)
  - SH-2: 36.363636 MB/s (read/write, 1 byte/cycle per SH-2)
  - 32X VDP: 29.488906 MB/s (14.148 MB/s read, 15.340906 MB/s write)
  - 68000: 1.917613 MB/s (read/write, 4 cycles/byte)
- Framebuffer fillrate: 18.181818 MPixels/s (16bpp), 36.363636 MPixels/s (8bpp)
  - SH-2: 18.181818 MPixels/s (16bpp), 36.363636 MPixels/s (8bpp)
  - 32X VDP: 7.670453 MPixels/s (16bpp), 15.340906 MPixels/s (8bpp)
  - 68000: 958,806 pixels/s (16bpp), 1.917613 MPixels/s (8bpp)
- 3D polygon geometry calculations:
  - Polygon transformations: 260,000 polygons/sec
  - Lighting calculations: 230,000 polygons/sec (flat), 180,000 polygons/sec (Gouraud)
- 3D polygon rendering:
  - Flat shading: 160,000 polygons/sec
  - Gouraud shading: 100,000 polygons/sec
  - Texture mapping: 50,000 polygons/sec
  - Texture Gouraud shading: 40,000 polygons/sec
- 2D sprite/tile capabilities: Scrolling, scaling, rotation, alpha blending
  - Colors per sprite/tile: 128 (8bpp), 256 (8bpp), 8192 (16bpp), 32,768 (16bpp)
  - Tile size: 8×8 texels, 64 bytes (8bpp), 128 bytes (16bpp)
  - Sprite sizes: 8×8 to 320×240 texels, 64 bytes to 150 KB
  - Maximum sprites/tiles per frame: 3800 sprites/tiles (8bpp, 8×8, 237.5 KB), 1900 sprites/tiles (16bpp, 8×8, 237.5 KB)
  - Maximum sprites/tiles per scanline: 1463 texels, 182 sprites/tiles (8×8)
Overlay/Underlay
- Overlay/Underlay graphics processors:
  - Genesis VDP — 13.423294 MHz (NTSC), 13.300856 MHz (PAL), 8/16-bit data bus
  - Sega CD ASIC — 12.5 MHz, 32-bit (2x 16-bit) data bus
- Overlay/Underlay Genesis VDP planes: 512–1536 color palette, 61–512 colors on screen
  - Sprite plane: 80 sprites/frame, 8×8 to 32×32 pixels/sprite, 16 colors/sprite, maximum 1280 sprite tiles/frame
  - Background planes: 2 tiled scrolling background layers, 8×8 pixels/tile, 16 colors/tile, 320×224 tilemaps, maximum 1808 tiles/frame
  - Fillrate: 6.934358 MPixels/s (read), 6.41376 MPixels/s (write), 6.934358–36.325644 MPixels/s (effective tile fillrate)
- Overlay/Underlay Sega CD ASIC planes: Enhanced Mega Drive VDP planes, enhanced FMV plane
  - Sprite/Tile planes: 128–1536 colors on screen, sprite/tile scaling and rotation
  - FMV plane: Full motion video, 32,768 colors on screen
  - Fillrate: 6.934358 MPixels/s (read/write), 6.934358–36.325644 MPixels/s (effective tile fillrate)

Sound
- Sound chip: QSound PWM @ 23.01136 MHz (NTSC), 22.801467 MHz (PAL)
  - Stereo PWM (Pulse Wave Modulation) mixing with Mega Drive sound; additional 2 channels (12 channels in total)
  - 11-bit PWM, stereo PCM output, surround sound

Memory
- System RAM: 648.5–1368.5 KB total, 512 KB (4 MBit) additional RAM to Mega Drive or Sega CD memory
  - Main RAM: 256 KB SDRAM
  - VRAM: 256 KB FPM DRAM (dual 128 KB framebuffers)
  - Genesis RAM: 136 KB (64 KB main, 64 KB video, 8 KB sound)
  - Sega CD RAM: 856 KB (512 KB main, 256 KB video, 64 KB audio)
- RAM Clear Hardware: 512 bytes (used for flat-shaded polygons)
- Internal processor cache: 5 KB
  - SH-2: 4 KB (2 KB per CPU)
  - 32X VDP: 1 KB, including 512 bytes (256 words) color palette RAM (CRAM)
- Cartridge ROM: 4–8 MB

Bandwidth
- System RAM bandwidth: 118.749992 MB/s (NTSC), 118.330206 MB/s (PAL), 3 data buses, 48-bit data bus width
  - SDRAM: 46.02272 MB/s (NTSC, 16-bit, 23.01136 MHz, 43ns), 45.602934 MB/s (PAL, 16-bit, 22.801467 MHz, 43ns)
  - VRAM: 72.727272 MB/s (32-bit, 18.181818 MHz, 55 ns, 16-bit per framebuffer, 36.363636 MB/s per framebuffer, 55ns cycles, 80ns access)
- Cartridge bandwidth:
  - Game ROM: 13.333333 MB/s (16-bit, 6.666666 MHz, 150 ns) to 28.571428 MB/s (16-bit, 14.285714 MHz, 70 ns)
  - Non-volatile SRAM: 6.666666 MB/s (6.666666 MHz, 150 ns) to 14.285714 MB/s (14.285714 MHz, 70 ns)
- Internal processor cache bandwidth:
  - SH-2: 184.09088 MB/s (92.04544 MB/s per SH-2, 32-bit per SH-2)
  - 32X VDP: 92.04544 MB/s (32-bit, 23.01136 MHz), including 46.02272 MB/s (16-bit, 23.01136 MHz) color palette RAM

External Links[]

Sega 32X technical specifications on segaretro.org