Sega Mega-CD/Technical specifications

Back to: Sega Mega-CD.

Technical specifications for the Sega Mega-CD.

CPU

Main CPU: Motorola 68000 16-bit processor running at 12.5 MHz

Same as the Mega Drive. Acts as a co-processor along with the Mega Drive CPU.
Bus width: 16-bit
Instruction set: 16-bit and 32-bit instructions, 16 registers
Performance: 2.19 MIPS

Co-processor: Motorola 68000 (Mega Drive CPU) running at 7.67 MHz

Bus width: 16-bit
Performance: 1.34225 MIPS

Graphics

GPU graphics processor: Sega 315-5548 Custom ASIC^[1]

Bus width: 32-bit (2x 16-bit)
Bus clock rate: 6.25 MHz (25 MB/s bandwidth)

Number of simultaneous colors on screen: 64 (default)

Using programming tricks, this limit is increased to 128–256 colors via raster effects.
128–256 colors can be displayed on screen using HAM techniques^[2]

Planes: 5 layers

Sega CD FMV layer
3 enhanced Mega Drive layers (sprite layer, 2 tile layers)
Mega Drive back screen

Full motion video: Video size from 1/4 to full screen, advanced compression scheme, software-based upgrade

On-screen colors available in Cinepak and TruVideo modes: 128–256 colors

Sprites/Tilemaps: The Mega-CD features enhancement effects such as scaling and rotation, similar to Sega's Super Scaler arcade hardware and that of the "Mode 7" effect employed by the Super NES. While Mode 7 only supports the scaling and rotation of tilemap backgrounds, the Sega CD supports the scaling and rotation of both the sprites and the tilemap backgrounds.^[3]
DMA transfer rates: 3.467179 MB/s (VRAM), 6.934358 MB/s (CRAM/VSRAM)

Transfer rates during active display: 1.625 MB/s (VRAM), 3.25 MB/s (CRAM/VSRAM)

Read/Write fillrate: 6.934358 MPixels/s

Write fillrate during active display: 3.25 MPixels/s

3D polygon graphics:^[4]

Vertex transformations: 16,000 vertices/sec^{[n 1]}
Polygon transformations: 5000 triangles/sec,^{[n 2]} 4000 quads/sec^{[n 3]}
Framebuffer rendering: 256×160, double-buffered, 15–30 FPS^{[n 4]}
Flat shading: 3300 polygons/sec (32-pixel triangles),^{[n 5]} 2100 polygons/sec (64-pixel quads)^{[n 6]}
Texture mapping: 2000 polygons/sec^{[n 7]}

Audio

The Mega-CD adds 10 sound channels to the 10 provided by the Mega Drive's sound chips.

CD Digital Audio

2-channel stereo
44.1 kHz sampling rate
16-bit PCM audio depth

Ricoh RF5C164 (315-5476A) PCM chip provides 8 sound channels.^[5]^[1]

Sound format: 8-bit sign/magnitude monaural PCM (with "stereo" support by allowing each channel to have different volumes on both left and right channels)
Maximum sample rate: 32 kHz
PCM audio depth: 16-bit^[3]
Bus width: 8-bit

Other specifications:

16-bit DAC
8x internal over-sampling digital filter
Frequency Range: 20 Hz - 20 KHz
Signal-to-Noise Ratio: > 90 dB @ 1K
Channel Separation: > 90 dB
Input: Mixer cable for Mega Drive Model 1 compatibility.
Output: Stereo RCA connectors.

Memory

System RAM: 856 KB^[6]

Main RAM: 4 Mbit (512 KB)
VRAM: 2 Mbit (256 KB)
PCM audio samples: 512 Kbit (64 KB)
CD-ROM data cache: 128 Kbit (16 KB)
Internal Backup RAM: 64 Kbit (8 KB)

System Boot ROM: 1 Mbit (128 KB)
External Memory Card: 1 Mbit (128 KB) CD BackUp RAM Cart
System RAM bandwidth: 62.5 MB/sec (3 buses, 56-bit bus width)^[6]

Main RAM: 25 MB/sec (16-bit, 12.5 MHz, FPM DRAM)^[7]
VRAM: 25 MB/sec (32-bit, 6.25 MHz, PSRAM)^[8]
Audio RAM: 12.5 MB/sec (8-bit, 12.5 MHz, SRAM)^[9]

Storage

500 MB CD-ROM discs (equivalent to 62 min of audio data)
Access time: 800 ms
1/4 screen B/W footage video: 1.5 to 4 hours
1/4 screen color footage: 45 minutes
CD-ROM drive transfer rate: 150 Kbytes/s (1x)

(Above specs prior to compression)

Boot ROM

Main article: Sega Mega-CD/Boot ROM.

Size: 1 Mb (128 KB)
Used for games, CD player, CD+G viewing, karaoke (limited to Japanese systems) and regional lockout

Other

Dimensions: 301 mm (11.85") x 212.5 mm (8.366") x 112.5 mm (4.429")
Mass: 1.4 kg (3lb 1.384oz)

Notes

↑ [767 cycles per vertex 767 cycles per vertex]
↑ [2301 cycles per triangle polygon 2301 cycles per triangle polygon]
↑ [3068 cycles per quad polygon 3068 cycles per quad polygon]
↑ [40 KB memory, 614.4 KB/s (15 FPS) to 1.2288 MB/s (30 FPS) bandwidth, 2.383275 CPU cycles per byte VRAM DMA transfer, 1.464285 MHz (15 FPS) to 2.928568 MHz (30 FPS) DMA, 9.571432 MHz (30 FPS) to 11.035715 MHz (15 FPS) remaining for polygons 40 KB memory, 614.4 KB/s (15 FPS) to 1.2288 MB/s (30 FPS) bandwidth, 2.383275 CPU cycles per byte VRAM DMA transfer, 1.464285 MHz (15 FPS) to 2.928568 MHz (30 FPS) DMA, 9.571432 MHz (30 FPS) to 11.035715 MHz (15 FPS) remaining for polygons]
↑
[32-pixel polygons, 15 FPS, scanline rendering, 250 cycles/scanline per poly, 3301 cycles/poly (4 scanlines)
- Polygon memory: 40 bytes per polygon, 8.594 KB memory (220 polygons per frame), 132 KB/s bandwidth (3300 polygons/sec)
32-pixel polygons, 15 FPS, scanline rendering, 250 cycles/scanline per poly, 3301 cycles/poly (4 scanlines)
- Polygon memory: 40 bytes per polygon, 8.594 KB memory (220 polygons per frame), 132 KB/s bandwidth (3300 polygons/sec)]
↑ [64-pixel polygons, 15 FPS, 250 cycles/scanline per poly, 5068 cycles/poly (8 scanlines) 64-pixel polygons, 15 FPS, 250 cycles/scanline per poly, 5068 cycles/poly (8 scanlines)]
↑
[ASIC's sprite/texture scaling and rotation capabilities can be used for texture mapping rasterization
- CPU cycles: 2 ASIC command cycles per texel, 128 ASIC command cycles per 8×8 texel texture, 77 cycles DMA transfer (32 bytes) per 8×8 texel texture, 5273 cycles (205 texture cycles) per 8×8 texel polygon
- Polygon/Texture memory: 72 bytes per textured polygon, 9.844 KB memory (140 polygons per frame), 151.2 KB/s bandwidth (2100 polygons/sec)
ASIC's sprite/texture scaling and rotation capabilities can be used for texture mapping rasterization
- CPU cycles: 2 ASIC command cycles per texel, 128 ASIC command cycles per 8×8 texel texture, 77 cycles DMA transfer (32 bytes) per 8×8 texel texture, 5273 cycles (205 texture cycles) per 8×8 texel polygon
- Polygon/Texture memory: 72 bytes per textured polygon, 9.844 KB memory (140 polygons per frame), 151.2 KB/s bandwidth (2100 polygons/sec)]

References

Sega Mega-CD
Topics	Technical specifications \| History \| Magazine articles \| Promotional material
Hardware	Mega CD (Asia \| North America \| Western Europe \| Eastern Europe \| South America \| Australasia \| Africa) Sega Multi-Mega (Asia \| North America \| Europe \| South America \| Australasia) Wondermega \| LaserActive \| CSD-G1M
Misc. hardware	CD BackUp RAM Cart \| Mega-CD Karaoke \| Pro CDX
Development tools	SNASM Mega-CD \| PsyQ Mega-CD SDK \| PSY-Q CD Emulation System (Mega-CD)
Unreleased hardware	Game Genie

[767_cycles_per_vertex-5] [767 cycles per vertex 767 cycles per vertex]

[2301_cycles_per_triangle_polygon-6] [2301 cycles per triangle polygon 2301 cycles per triangle polygon]

[3068_cycles_per_quad_polygon-7] [3068 cycles per quad polygon 3068 cycles per quad polygon]

[40_KB_memory.2C_614.4_KB.2Fs_.2815_FPS.29_to_1.2288_MB.2Fs_.2830_FPS.29_bandwidth.2C_2.383275_CPU_cycles_per_byte_VRAM_DMA_transfer.2C_1.464285_MHz_.2815_FPS.29_to_2.928568_MHz_.2830_FPS.29_DMA.2C_9.571432_MHz_.2830_FPS.29_to_11.035715_MHz_.2815_FPS.29_remaining_for_polygons-8] [40 KB memory, 614.4 KB/s (15 FPS) to 1.2288 MB/s (30 FPS) bandwidth, 2.383275 CPU cycles per byte VRAM DMA transfer, 1.464285 MHz (15 FPS) to 2.928568 MHz (30 FPS) DMA, 9.571432 MHz (30 FPS) to 11.035715 MHz (15 FPS) remaining for polygons 40 KB memory, 614.4 KB/s (15 FPS) to 1.2288 MB/s (30 FPS) bandwidth, 2.383275 CPU cycles per byte VRAM DMA transfer, 1.464285 MHz (15 FPS) to 2.928568 MHz (30 FPS) DMA, 9.571432 MHz (30 FPS) to 11.035715 MHz (15 FPS) remaining for polygons]

[32-pixel_polygons.2C_15_FPS.2C_.5B.5Bwikipedia:Scanline_rendering.7Cscanline_rendering.5D.5D.2C_250_cycles.2Fscanline_per_poly.2C_3301_cycles.2Fpoly_.284_scanlines.29.0A.2A_Polygon_memory:_40_bytes_per_polygon.2C_8.594_KB_memory_.28220_polygons_per_frame.29.2C_132_KB.2Fs_bandwidth_.283300_polygons.2Fsec.29-9] [32-pixel polygons, 15 FPS, scanline rendering, 250 cycles/scanline per poly, 3301 cycles/poly (4 scanlines)
Polygon memory: 40 bytes per polygon, 8.594 KB memory (220 polygons per frame), 132 KB/s bandwidth (3300 polygons/sec)
32-pixel polygons, 15 FPS, scanline rendering, 250 cycles/scanline per poly, 3301 cycles/poly (4 scanlines)
Polygon memory: 40 bytes per polygon, 8.594 KB memory (220 polygons per frame), 132 KB/s bandwidth (3300 polygons/sec)]

[6] Polygon memory: 40 bytes per polygon, 8.594 KB memory (220 polygons per frame), 132 KB/s bandwidth (3300 polygons/sec)

[7] Polygon memory: 40 bytes per polygon, 8.594 KB memory (220 polygons per frame), 132 KB/s bandwidth (3300 polygons/sec)]

[64-pixel_polygons.2C_15_FPS.2C_250_cycles.2Fscanline_per_poly.2C_5068_cycles.2Fpoly_.288_scanlines.29-10] [64-pixel polygons, 15 FPS, 250 cycles/scanline per poly, 5068 cycles/poly (8 scanlines) 64-pixel polygons, 15 FPS, 250 cycles/scanline per poly, 5068 cycles/poly (8 scanlines)]

[ASIC.27s_sprite.2Ftexture_scaling_and_rotation_capabilities_can_be_used_for_texture_mapping_rasterization.0A.2ACPU_cycles:_2_ASIC_command_cycles_per_texel.2C_128_ASIC_command_cycles_per_8.C3.978_texel_texture.2C_77_cycles_DMA_transfer_.2832_bytes.29_per_8.C3.978_texel_texture.2C_5273_cycles_.28205_texture_cycles.29_per_8.C3.978_texel_polygon.0A.2APolygon.2FTexture_memory:_72_bytes_per_textured_polygon.2C_9.844_KB_memory_.28140_polygons_per_frame.29.2C_151.2_KB.2Fs_bandwidth_.282100_polygons.2Fsec.29-11] [ASIC's sprite/texture scaling and rotation capabilities can be used for texture mapping rasterization
CPU cycles: 2 ASIC command cycles per texel, 128 ASIC command cycles per 8×8 texel texture, 77 cycles DMA transfer (32 bytes) per 8×8 texel texture, 5273 cycles (205 texture cycles) per 8×8 texel polygon

Polygon/Texture memory: 72 bytes per textured polygon, 9.844 KB memory (140 polygons per frame), 151.2 KB/s bandwidth (2100 polygons/sec)
ASIC's sprite/texture scaling and rotation capabilities can be used for texture mapping rasterization
CPU cycles: 2 ASIC command cycles per texel, 128 ASIC command cycles per 8×8 texel texture, 77 cycles DMA transfer (32 bytes) per 8×8 texel texture, 5273 cycles (205 texture cycles) per 8×8 texel polygon

Polygon/Texture memory: 72 bytes per textured polygon, 9.844 KB memory (140 polygons per frame), 151.2 KB/s bandwidth (2100 polygons/sec)]

[10] CPU cycles: 2 ASIC command cycles per texel, 128 ASIC command cycles per 8×8 texel texture, 77 cycles DMA transfer (32 bytes) per 8×8 texel texture, 5273 cycles (205 texture cycles) per 8×8 texel polygon

[11] Polygon/Texture memory: 72 bytes per textured polygon, 9.844 KB memory (140 polygons per frame), 151.2 KB/s bandwidth (2100 polygons/sec)

[12] CPU cycles: 2 ASIC command cycles per texel, 128 ASIC command cycles per 8×8 texel texture, 77 cycles DMA transfer (32 bytes) per 8×8 texel texture, 5273 cycles (205 texture cycles) per 8×8 texel polygon

[13] Polygon/Texture memory: 72 bytes per textured polygon, 9.844 KB memory (140 polygons per frame), 151.2 KB/s bandwidth (2100 polygons/sec)]

[:File:MCD_MaintenanceManual_Export_RevA.pdf_p102-1] 1.0 ^1.1 File:MCD MaintenanceManual Export RevA.pdf, page 102

[.5Bhttps:.2F.2Fbooks.google.co.uk.2Fbooks.3Fid.3DdeBFx7QAwsQC.26pg.3DPA556.23v.3Donepage.26q.26f.3Dfalse_Encyclopedia_of_Video_Games.5D-2] Encyclopedia of Video Games

[Sega_CD_programming_FAQ_.281998-12-06.29-3] 3.0 ^3.1 Sega CD programming FAQ (1998-12-06)

[.5Bhttps:.2F.2Fwww.youtube.com.2Fwatch.3Fv.3DVyme7CT04cw_GASEGA68k.27s_Genesis_Fully_3D_Star_Fox_Demo:_Stock_and_12_MHz_Overclock.5D.2C_YouTube-4] GASEGA68k's Genesis Fully 3D Star Fox Demo: Stock and 12 MHz Overclock, YouTube

[:File:MCDHardware_Manual_PCM_Sound_Source.pdf_p-12] File:MCDHardware Manual PCM Sound Source.pdf

[:File:MCD_MaintenanceManual_Export_RevA.pdf_p-13] 6.0 ^6.1 File:MCD MaintenanceManual Export RevA.pdf

[:File:TC511664B_datasheet.pdf_p-14] File:TC511664B datasheet.pdf

[:File:TC51832_datasheet.pdf_p-15] File:TC51832 datasheet.pdf

[:File:MB8464A_datasheet_2.pdf_p-16] File:MB8464A datasheet 2.pdf

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