Difference between revisions of "Sega Mega-CD/Technical specifications"

From Sega Retro

(→‎Graphics: GPU is the same VDP as in the Mega Drive; GFX merely provides transformations. There's no "FMV layer"; this is simply one of the scroll planes. None of the VDP layers are "enhanced".)
(→‎Graphics: Removed 3D polygon graphics entirely. This was for a base Mega Drive homebrew demo and doesn't involve Mega CD at all.)
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* Read/Write fillrate: 6.934358 MPixels/s
 
* Read/Write fillrate: 6.934358 MPixels/s
 
:* Write fillrate during active display: 3.25 MPixels/s
 
:* Write fillrate during active display: 3.25 MPixels/s
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* 3D polygon graphics:{{ref|1=[https://www.youtube.com/watch?v=Vyme7CT04cw GASEGA68k's Genesis Fully 3D Star Fox Demo: Stock and 12 MHz Overclock], YouTube}}
 
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:* Vertex transformations: 16,000 vertices/sec{{ref|767 cycles per vertex|group=n}}
 
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:* Polygon transformations: 5000 triangles/sec,{{ref|2301 cycles per triangle polygon|group=n}} 4000 quads/sec{{ref|3068 cycles per quad polygon|group=n}}
 
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:* Framebuffer rendering: 256×160, double-buffered, 15–30 FPS{{ref|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|group=n}}
 
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:* Flat shading: 3300 polygons/sec (32-pixel triangles),{{ref|32-pixel polygons, 15 FPS, [[wikipedia:Scanline rendering|scanline rendering]], 250 cycles/scanline per poly, 3301 cycles/poly (4 scanlines)
 
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* Polygon memory: 40 bytes per polygon, 8.594 KB memory (220 polygons per frame), 132 KB/s bandwidth (3300 polygons/sec)
 
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|group=n}} 2100 polygons/sec (64-pixel quads){{ref|64-pixel polygons, 15 FPS, 250 cycles/scanline per poly, 5068 cycles/poly (8 scanlines)|group=n}}
 
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:* Texture mapping: 2000 polygons/sec{{ref|ASIC's sprite/texture scaling and rotation capabilities can be used for texture mapping rasterization
 
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*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
 
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*Polygon/Texture memory: 72 bytes per textured polygon, 9.844 KB memory (140 polygons per frame), 151.2 KB/s bandwidth (2100 polygons/sec)
 
 
|group=n}}
 
|group=n}}
 
}}
 
}}

Revision as of 19:00, 26 January 2023

Back to: Sega Mega-CD.

Technical specifications for the Sega Mega-CD.

The following are upgrades over the Sega Mega Drive technical specifications.

See Sega Mega Drive technical specifications for details of the base Mega Drive hardware

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

  • Bus width: 32-bit (2x 16-bit)
  • Bus clock rate: 6.25 MHz (25 MB/s bandwidth)
  • Transformed graphics tiles are DMA'd to the main VRAM for display.
  • 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.[2]
  • 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

}}

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
  • 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[2]
  • 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

  • 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)[4]
  • Main RAM: 25 MB/sec (16-bit, 12.5 MHz, FPM DRAM)[5]
  • VRAM: 25 MB/sec (32-bit, 6.25 MHz, PSRAM)[6]
  • Audio RAM: 12.5 MB/sec (8-bit, 12.5 MHz, SRAM)[7]

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

References

  1. ↑ 1.0 1.1 File:MCD MaintenanceManual Export RevA.pdf, page 102
  2. ↑ 2.0 2.1 Sega CD programming FAQ (1998-12-06)
  3. ↑ File:MCDHardware Manual PCM Sound Source.pdf
  4. ↑ 4.0 4.1 File:MCD MaintenanceManual Export RevA.pdf
  5. ↑ File:TC511664B datasheet.pdf
  6. ↑ File:TC51832 datasheet.pdf
  7. ↑ File:MB8464A datasheet 2.pdf


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
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