View source for Sega Mega-CD/Technical specifications

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Technical specifications for the [[Sega Mega-CD]].

__TOC__

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

==CPU==
{{multicol|
* 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 [[wikipedia:Instructions per second|MIPS]]
* Co-processor: Motorola 68000 (Mega Drive CPU) running at 7.67 MHz
** Bus width: 16-bit
** Performance: 1.34225 MIPS
}}

==Graphics==
{{multicol|
* GPU graphics processor: Sega 315-5548 Custom [[wikipedia:ASIC|ASIC]]{{fileref|MCD MaintenanceManual Export RevA.pdf|page=102}}
** Bus width: 32-bit (2x 16-bit)
** Bus clock rate: 6.25 MHz (25 MB/s bandwidth)
* Number of simultaneous [[Palette|colors]] on screen: 64 (default)
** Using programming tricks, this limit is increased to 128–256 colors via raster effects. 
** 128&ndash;256 colors can be displayed on screen using [[wikipedia:Hold-And-Modify|HAM]] techniques{{ref|1=[https://books.google.co.uk/books?id=deBFx7QAwsQC&pg=PA556#v=onepage&q&f=false Encyclopedia of Video Games]}}
* 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
* [[Sprite]]s/[[wikipedia:Tile engine|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.{{intref|Sega CD programming FAQ (1998-12-06)}}
* 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:{{ref|[https://www.youtube.com/watch?v=Vyme7CT04cw GASEGA68k's Genesis Fully 3D Star Fox Demo: Stock and 12 MHz Overclock], YouTube}}
** Vertex transformations: 16,000 vertices/sec{{ref|767 cycles per vertex|group=n}}
** Polygon transformations: 5000 triangles/sec,{{ref|2301 cycles per triangle polygon|group=n}} 4000 quads/sec{{ref|3068 cycles per quad polygon|group=n}} 
** 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}}
** 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)
* Polygon memory: 40 bytes per polygon, 8.594 KB memory (220 polygons per frame), 132 KB/s bandwidth (3300 polygons/sec)
|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}}
** Texture mapping: 2000 polygons/sec{{ref|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)
|group=n}}
}}

==Audio==
{{multicol|
''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:{{fileref|MCD MaintenanceManual Export RevA.pdf|page=102}}
** 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{{intref|Sega CD programming FAQ (1998-12-06)}}
** 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 jack|RCA]] connectors.
}}

==Memory==
{{multicol|
* System [[RAM]]: 856 KB{{fileref|MCD MaintenanceManual Export RevA.pdf}}
** Main RAM: 4 [[Bit|Mbit]] (512 KB)
** [[VRAM]]: 2 Mbit (256 KB)
** PCM audio samples: 512 [[Bit|Kbit]] (64 KB)
** CD-ROM data cache: 128 Kbit (16 KB)
** Internal Backup RAM: 64 Kbit (8 KB)
* System [[BIOS|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){{fileref|MCD MaintenanceManual Export RevA.pdf}}
** Main RAM: 25 MB/sec (16-bit, 12.5 MHz, [[wikipedia:FPM DRAM|FPM DRAM]]){{fileref|TC511664B datasheet.pdf}}
** VRAM: 25 MB/sec (32-bit, 6.25 MHz, [[wikipedia:PSRAM|PSRAM]]){{fileref|TC51832 datasheet.pdf}}
** Audio RAM: 12.5 MB/sec (8-bit, 12.5 MHz, [[SRAM]]){{fileref|MB8464A datasheet 2.pdf}}
}}

==Storage==
{{multicol|
* 500 MB CD-ROM discs (equivalent to 62 min of audio data)
* Access time: 800 [[wikipedia:Microsecond|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)''
}}

==[[BIOS|Boot ROM]]==
* Size: 1 Mb (128 KB)
* Used for games, CD player, CD+G viewing, karaoke (limited to Japanese systems) and regional lockout
* Region codes: "NA" <nowiki>=</nowiki> North America (NTSC), "EU" <nowiki>=</nowiki> Europe (PAL)

{| class="prettytable"
|+ Boot ROM Revisions
|-
! width="50"| Boot ROM Version
! Machine
! Download
! CRC32
|-
| rowspan="2"| 0.98
| rowspan="2"| Pioneer LaserActive
| {{file|Us lsr 930329.zip|0.98 (NA)}}
| 8c3e3945
|-
| {{file|Jp lsr 930329.zip|0.98 (Asia)}}
| 9f5771d2
|-
| rowspan="9"| 1.00
| rowspan="9"| Sega/Mega CD Model 1<br/>Victor WonderMega 1 (Asia)<br/>Sega WonderMega (Asia)
| {{file|BIOS Mega CD Japan 1.00g.7z|1.00g (Asia, NTSC)}}
| 3beb1ac2
|-
| {{file|BIOS Mega CD Japan 1.00l.md.zip|1.00l (Asia, NTSC)}}
| f18dde5b
|-
| {{file|BIOS Mega CD Japan v1.00o.7z|1.00o (Asia, NTSC)}}
| 1d9756a3
|-
| {{file|Jp mcd1 911217.zip|1.00p (Asia, NTSC)}}
| 9d2da8f2
|-
| {{file|BIOS Mega CD Japan 1.00S.md.zip|1.00s (Asia, NTSC)}}
| 79f85384
|-
| {{file|Jp mcd1 911228.zip|1.00s (Asia, PAL)}}
| 550f30bb
|-
| {{file|Jp wmg 920206.zip|1.00w (Sega WonderMega Bios)}}
| d21fe71d
|-
| {{file|BIOS Sega CD USA 1.00.md.zip|1.00 (NA)}}
| e7e3afe2
|-
| {{file|Eu mcd1 921027.zip|1.00 (EU)}}
| 529ac15a
|-
| 1.04
| Pioneer LaserActive
| {{file|Us mld 930922.zip|1.04 (NA)}}
| 2ed602d7
|-
| 1.05
| Pioneer LaserActive
| {{file|Jp lsr 930810.zip|1.05 (Asia)}}
| b24b919d
|-
| 1.10
| Sega CD Model 1 (minor update)
| {{file|Us scd1 921011.zip|1.10 (NA)}}
| c6d10268
|-
| 1.11
| Mega CD Model 2 (Japan sample/prototype)
| {{file|Jp mcd2 920501.zip|1.11 (JP)}}
| 4be18ff6
|-
| rowspan="7"| 2.00
| rowspan="7"| Sega/Mega CD 2<br/>Victor WonderMega 2 (Asia)<br/>JVC X'Eye (NA)
| {{file|Us scd2 930314.zip|2.00 (1<sup>st</sup> NA version)}}
| 8af65f58
|-
| {{file|Us scd2 930601.zip|2.00w (2<sup>nd</sup> NA version)}}
| 9f6f6276
|-
| {{file|Jp mcd2 921222.zip|2.00c (Asian version)}}
| dd6cc972
|-
| {{file|Eu mcd2 930330.zip|2.00 (1<sup>st</sup> EU version)}}
| 0507b590
|-
| {{file|Eu mcd2 930601.zip|2.00w (2<sup>nd</sup> EU version)}}
| 4d5cb8da
|-
| {{file|Us xeye 931227.zip|2.00 (X'Eye)}}
| 290f8e33
|-
| {{file|Wondermega 2.00 Bios.zip|2.00 (Wondermega)}}
| 2b19972f<sup>1</sup>
|-
| rowspan="2"| 2.11
| rowspan="2" | Sega/Mega CD 2, Aiwa CSD G1M (Japan)
| {{file|Us scd2 930621.zip|2.11w (NA)}}
| 2e49d72c
|-
| {{file|Aiwa_CSD_GM1_Bios.zip|2.11c (JP)}}
| 12154531
|-
| rowspan="2"| 2.21
| rowspan="2"| Sega Multimega (Europe & Japan), CDX (North America), Linguaphone Education Gear (Japan)
| {{file|Eu mmg 930916.zip|2.21x (MultiMega, EU)}}
| aacb851e
|-
| {{file|Us cdx 930907.zip|2.21x (CDX)}}
| d48c44b5
|}

<sup>1</sup> The ZIP file contains two dumps, a "good" dump and a "bad" dump. The "bad" dump has an incorrect HINT vector, but is otherwise identical to the "good" dump. The CRC32 listed here is for the "good" dump.

==Other==
*Dimensions: 301mm x 212.5 x 112.5
*Weight: 1.4 kg (3.1 lbs)

==Notes==
{{multicol|
<references group="n"/>
|cols=2}}

==References==
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<references />
|cols=3}}

{{MegaCD}}

[[Category:Sega Mega-CD|Technical specifications]]