Sega Mega-CD/Technical specifications

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

• GPU: Same as base Mega Drive
• GFX co-processor: Sega 315-5548 Custom ASIC

• 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.
• 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

• Ricoh RF5C164 (315-5476A) PCM chip provides 8 sound channels.

• 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
• 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

• 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)

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

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)