Difference between revisions of "Sega Mega Drive"

From Sega Retro

(Note about reference 10.0: the reference itself says that IRQ2 is used by System C2, not by the MD. Anyone?)
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==Technical specifications==
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===Technical specifications===
 
* System master clock rate: 53.693175 MHz ([[NTSC]]), 53.203424 MHz ([[PAL]]) {{fileref|Sega Service Manual - Genesis II - Mega Drive II (PAL) - 001 - June 1993.pdf}}
 
* System master clock rate: 53.693175 MHz ([[NTSC]]), 53.203424 MHz ([[PAL]]) {{fileref|Sega Service Manual - Genesis II - Mega Drive II (PAL) - 001 - June 1993.pdf}}
 
** Master clock cycles per frame: 896,040 (NTSC), 1,067,040 (PAL)
 
** Master clock cycles per frame: 896,040 (NTSC), 1,067,040 (PAL)
 
** Master clock cycles per scanline: 3420 {{ref|https://github.com/ekeeke/Genesis-Plus-GX/blob/master/core/system.h}}
 
** Master clock cycles per scanline: 3420 {{ref|https://github.com/ekeeke/Genesis-Plus-GX/blob/master/core/system.h}}
  
===CPU===
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====Processors====
 
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* Main CPU: [[Motorola]] [[68000]]
 
* Main CPU: [[Motorola]] [[68000]]
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===Sound===
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====Sound====
 
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* FM [[wikipedia:Sound chip|sound chip]]: [[Yamaha]] [[YM2612]], clocked at the 68000 clock speed (7.6705 MHz in NTSC, 7.61 MHz in PAL)
 
* FM [[wikipedia:Sound chip|sound chip]]: [[Yamaha]] [[YM2612]], clocked at the 68000 clock speed (7.6705 MHz in NTSC, 7.61 MHz in PAL)
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===Graphics===
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====Graphics====
 
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* [[wikipedia:Graphics processing unit|GPU]] chipset:
 
* [[wikipedia:Graphics processing unit|GPU]] chipset:
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===Memory===
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====Memory====
 
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* System RAM: 136 [[Byte|KB]]
 
* System RAM: 136 [[Byte|KB]]
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====Configuration====
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=====Configuration=====
 
* System memory buses: {{fileref|Sega Service Manual - Genesis II - Mega Drive II (PAL) - 001 - June 1993.pdf}}
 
* System memory buses: {{fileref|Sega Service Manual - Genesis II - Mega Drive II (PAL) - 001 - June 1993.pdf}}
 
** 16‑bit system bus &mdash; 68000 & VDP <‑> Main RAM & Cartridge ROM/RAM
 
** 16‑bit system bus &mdash; 68000 & VDP <‑> Main RAM & Cartridge ROM/RAM
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====Bandwidth====
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=====Bandwidth=====
 
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* Internal processor bandwidth:
 
* Internal processor bandwidth:
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===Memory map===
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====Memory map====
 
{| class="wikitable" border="1"
 
{| class="wikitable" border="1"
 
|+ Mega Drive Memory Map
 
|+ Mega Drive Memory Map
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|}
 
|}
  
===Input===
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====Input====
 
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{{multicol|
 
* Controller input: Two male [[DE-9|DE‑9]] controller ports; one female [[DE‑9]] expansion port (early MD1s only)
 
* Controller input: Two male [[DE-9|DE‑9]] controller ports; one female [[DE‑9]] expansion port (early MD1s only)
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====Sega CD====
 
====Sega CD====
:''See [[Sega Mega-CD#Technical Specifications|Sega Mega-CD technical specifications]].''
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:''See [[Sega Mega-CD#Technical specifications|Sega Mega-CD technical specifications]].''
  
 
The [[Sega CD]] (Mega CD) add‑on, released in 1991, adds the following specifications:
 
The [[Sega CD]] (Mega CD) add‑on, released in 1991, adds the following specifications:

Revision as of 01:12, 31 May 2016

Megadrive1.jpgMegadrive2.jpg
Sega Mega Drive
Manufacturer: Sega
Variants: Mega Drive 2, Genesis 3, Mega Jet, Nomad, AtGames, Mega Tech, Mega Play, System C, System 18, Amstrad Mega PC, Al-Alamiah AX-660, Al-Alamiah AX-990
Add-ons: Mega-CD, 32X, Demo System DS-16, ERX 308P, ERX 318P, Master Mega Converter, MD 8bit Converter, Mega/Master Adaptor, Mega Modem, Power Base Converter, Pro MegaMaster, Sprobe, Super Magic Drive
Release Date RRP Code

The Sega Mega Drive (メガドライブ), called the Sega Genesis in North America and Super Gam*Boy (수퍼겜보이) (later Super Aladdin Boy (수퍼알라딘 보이) in South Korea, is a video game console developed by Sega in 1988. The Sega Mega Drive is Sega's third home console, following the SG-1000 (including SG-1000 II) and the Sega Master System (Mark III). It was codenamed the Sega Mark V during development and is part of what is now known as the fourth generation of video game consoles.

The Mega Drive is widely considered to be Sega's most successful video game console. It sold over 40 million consoles worldwide, according to Sega, including more than 20 million in the United States, over 9 million in Western Europe, 3.58 million in Japan, and 3 million in Brazil.

It also had a software library consisting of more than one thousand games released for the system in total. As well as competing with Nintendo's Famicom (NES) and later Super Famicom (SNES) for market control, Sega also found itself fighting against NEC's TurboGrafx-16 (PC Engine in Japan), SNK's Neo Geo, the Atari Jaguar and numerous home computers in one of the biggest "console wars" of all time.

The Mega Drive would be succeeded by the Sega Saturn (released in 1994), and then the Sega Dreamcast (released in 1998).

Hardware

The Mega Drive was envisioned at the next technological step over other video game consoles available at the time. It is a "16-bit" machine, named after its use of a 16-bit CPU (in this case, the Motorola 68000), and was marketed as being superior to popular "8-bit" consoles dominating the market at the time, usually the Nintendo Entertainment System (NES) but sometimes its immediate predecessor, the Sega Master System. 16-bit CPUs had been gaining popularity since the mid-80s, were widely used in arcade machines, and were almost expected to be found in new home computers - it was therefore considered logical that the next "generation" of dedicated video game consoles should follow suit.

The Mega Drive builds on technology found in the Master System (and with adaptors, is fully backwards compatible), though as well as upping the technical specifications for more demanding gameplay, sound and graphics, makes a number of cruicial changes to the design of consoles which continue to this day. Firstly it added a third face button, C, to the (now ergonomically designed) control pad. The Mega Drive outputs sound in stereo, and makes an attempt to region lock games through software. Also, when utilising the right cables, the Mega Drive is natively able to produce a clearer image than its rivals (on top of its already higher resolution 320x240 display).

All Mega Drives ultilise a top-loading design (as opposed to the cumbersome VCR-style cartridge loading of the Western NES), while having removable controllers (unlike the Famicom). It was designed from day one to allow hardware expansions, and its use of dark plastic means that the "yellowing" of older systems (from bromine-based flame retardants reacting with oxygen) is less of an issue.

Models

Main article: Mega Drive consoles.

Mega Drive

The original Mega Drive measures 28 cm×21.2 cm×7 cm. The top of the unit is split into two components: a circular emboss with the cartridge slot and a tagline (which was omitted on later versions), and a control panel containing the power and reset buttons and the volume slider for the headphones jack. Audio output through the original model was mono through the A/V port, while the headphone jack was used for stereo sound. A third DE-9 port on the back of the unit provided additional peripheral support, though was removed from later revisions.

Asian, Japanese and South Korean models have a cartridge locking mechanism which prevents cartridges from being removed when the power is on (which is why "Eastern" cartridges, as well as the Sonic & Knuckles cartridge and various others, have a cut-out on their left sides). Later runs included the TradeMark Security System, missing in early builds causing small compatibility issues, despite the feature having been planned early on.

Mega Drive 2

1993 saw this cost-reduced redesign (known as the Mega Drive II in Europe, and not explicitly referred to as anything other than "Genesis" in North America), at 22 cm×21.2 cm×5.9 cm, being introduced internationally. One of the major revisions from the original model was the removal of the headphones jack in favor of stereo output through a redesigned 9-pin A/V port. American and European models used a momentary switch for power while non-western models used a left-right switch. Furthermore, the audio mixing circuitry was modified, resulting in noticeably different quality audio output — here is a page with audio samples, provided by little-scale.

A common myth is that the Mega Drive 2 lacks a Z80 — the truth is that it lacks a Zilog Z80. During the Mega Drive's lifetime, Sega received various off-the-shelf chips from different manufacturers, and sometimes would rebrand chips as their own or make them themselves, which is what happened here (and which is why each Mega Drive has a different manufacturer for its 68000). If the Z80 was missing, most games would have no sound (or not all sound). In later revisions, the Z80 was integrated into a custom ASIC which also incorporated the major chips of the system.

Genesis 3

Main article: Genesis 3.
A Genesis 3.

The Genesis 3 was a small version manufactured by Majesco in 1998 for the American market, which they had been manufacturing for until then. It is much smaller than its predecessors and lacks all expansions and fixes memory controller bugs — both rendering some games unplayable and the Sega CD and 32X unusable.

Portables: Mega Jet and Nomad

Main articles: Sega Mega Jet and Sega Nomad.

The Mega Jet and Nomad were portable Mega Drive systems released near the middle/end of the system's lifetime. The Mega Jet, released in 1994, was originally designed for use on JAL airliners but was later released for Japanese consumers. The Mega Jet is a semi-portable system; the system has a built-in controller but requires an external power supply and a TV. The Nomad was a full portable in its own right, having an integrated screen and sound capabilities, in addition to a battery pack.

Arcade hardware: Mega Tech, Mega Play, and the System C

Main articles: Mega Tech, Mega Play, System C.

The Mega Drive hardware was adapted for arcade use several times over the course of its life. The Mega Tech and Mega Play allowed arcade operators to provide somewhat modified versions of popular Mega Drive games for arcade play — these systems use special cartridges containing games and players can choose from the games plugged into the system. The System C is a different board built from modified Mega Drive hardware, boasting improved color abilities and (in later revisions known collectively as the System C2) improved sample playback. The System C was primarily home to puzzle games — Columns and Puyo Puyo were released on this hardware.

Data East is also known to have licensed Mega Drive hardware for an arcade version of High Seas Havoc; not much is known about this board.

Mega-CD combos: JVC Wondermega/X'eye, Pioneer LaserActive, Sega Multi-Mega, and Aiwa Mega CD

Main articles: Wondermega, LaserActive, Sega Multi-Mega, Aiwa Mega CD.

Combination Mega Drive/Mega-CD units were developed over the course of the Mega-CD's lifetime. The Wondermega and LaserActive are standalone consoles; the LaserActive also plays LaserDiscs. The Multi-Mega is a portable audio CD player that can play Mega Drive and Mega-CD games when plugged in to wall power and a TV. The Aiwa Mega CD is a Mega Drive/Mega-CD packed into Aiwa's consumer-level portable CD stereos.

Computer combinations: Sega Teradrive, Amstrad Mega PC, al-Alamiah units

Main articles: Sega Teradrive, Amstrad Mega PC, Al-Alamiah AX-660, Al-Alamiah AX-990.

The Teradrive and Mega PC are combination Mega Drive/IBM-compatible PCs made for the Japanese and UK markets, respectively. The three Al-Alamiah computers are combination Mega Drive/MSX computers for the Arabic market.

Modern System-on-a-Chip compilations

A variety of companies now make licensed system-on-a-chip units in a variety of fashions that contain single-chip Mega Drive implementations and several licensed ROM images. TecToy-made SoaCs also contain several "new" MD games, however these are believed to be — and likely are — Java 2 Mobile Edition games running on additional hardware. For a full list of SoaCs, see the template at the bottom of the page.

Cartridges

The Mega Drive runs games housed in plastic cartridges uniquely shaped to fit the system. Though the technology exists to run Sega Master System games, the Power Base Converter is required to convert between the differing pin connections and slot sizes.

Official Mega Drive cartridges are generally smaller than their Master System/Mark III counterparts, with rounded edges and, in the case of "western" systems, bigger labels layered over the top and front of the cartridge. Region locking exists, albeit in a selection of rather crude forms - the TradeMark Security System, which is missing in many early Mega Drive systems, through software checks implemented manually by developers (which did not begin to feature in new releases until 1993), and differences in cartridge shape. Region locking is easily circumvented through the use of adapters - troubles only arise when dealing with 50Hz/60Hz differences between NTSC and PAL systems, leading some games to run too slowly while others, too fast.

As with the Master System, Sega-manufactured Japanese, Korean and Asian cartridges are shaped differently to those seen in North America, South America, Europe and Oceania, however the differences largely concern the aesthetics - "Eastern" Japanese-style cartridges opting for a more rounded approach with ridges, while "Western" cartridges being more angular and simplistic. Unlike the Master System, the Mega Drive has end-labels for easier reading and storage in western regions.

Pin layout is the same between the two types, however the base of the cartridge determines whether it can be safely inserted into the system - two extra pieces of plastic prevent Japanese cartridges from being inserted in western systems - these can be removed with modification, or as mentioned above, circumvented with adapters. This extra plastic is not present in systems such as the Genesis 3 and Sega 32X, nor does it exist in Japanese Mega Drives.

One interesting feature of Japanese cartridges is a inclusion of a cartridge "lock", which prevents the cartridge from being removed when the system turns on. A plastic piece from the system is slid across to a gap on the left hand side of a Japanese cartridge, securing it in place when the power switch is moved (similar tricks can be found on the Super NES and the TurboGrafx-16). This locking mechanism is only present in Japanese Model 1 Mega Drives and is absent in all western models - the vast majority of western cartridges lack the gap required for cartridge locking, with exceptions being the likes of "special" cartridges, e.g. Sonic & Knuckles.

The lack of cartridge lock can be exploited, for example, to gain access to the level selection screen in Sonic 3D Blast.

Official cartridge designs

Cartridge designs for Altered Beast - though labels would change dramatically over the console's run, the physical shape would remain consistent.

Alternative cartridge designs

Though Sega manufactured the bulk of Mega Drive cartridges, many were created externally by the likes of Electronic Arts, Accolade, Sunsoft and Codemasters.

Technical specifications

  • System master clock rate: 53.693175 MHz (NTSC), 53.203424 MHz (PAL) [1]
    • Master clock cycles per frame: 896,040 (NTSC), 1,067,040 (PAL)
    • Master clock cycles per scanline: 3420 [2]

Processors

  • Main CPU: Motorola 68000
    • Clock rate: 7.6705 MHz (NTSC), 7.61 MHz (PAL)
    • The 68000 has a 24‑bit address space, allowing access to up to 16 MB of memory. Sega's memory map for the Mega Drive allowed games to be up to 4 MB without the use of a memory mapper; games that tried to go up to 10 MB would find their memory maps crushed by the Sega CD (which took the second 4 MB block) and Sega 32X (which took 2 MB of the third 4 MB block). All devices are memory mapped.
      • Games using save memory also needed to have the memory in the cartridge map; larger games, such as Phantasy Star IV, used a mapper to swap out cart space for SRAM during a save.
    • Instruction set: 16‑bit and 32‑bit CISC instructions
    • Bus width: 16‑bit [3]
  • Sound CPU: Zilog Z80
    • Clock rate: 3.58 MHz (NTSC), 3.55 MHz (PAL)
    • Some games did not use the Z80, other games used it only for sample playback, but most used it for sound processing
    • 8 KB program RAM which the 68000 and the Z80 can freely write to (though the 68000 must request the Z80 bus)
    • Can access 32 KB of the 68000 memory map at once (while it should be used for accessing the cartridge, setting the bank register elsewhere can work on some hardware)
    • Instruction set: 8‑bit and 16‑bit instructions
    • Bus width: 8‑bit
  • CPU instruction performance: 1.8614 MIPS (NTSC), 1.8466 MIPS (PAL) [4]
    • 68000 performance: 1.3423 MIPS (NTSC), 1.3318 MIPS (PAL)
    • Z80 performance: 0.5191 MIPS (NTSC), 0.5148 MIPS (PAL)

Sound

  • FM sound chip: Yamaha YM2612, clocked at the 68000 clock speed (7.6705 MHz in NTSC, 7.61 MHz in PAL)
    • 6 channels of FM synthesis, Operator Type‑N
      • The third channel can enter a Special Mode, or multifrequency mode, where each individual operator has a different frequency
      • The sixth channel can enter a DAC mode where the sound program constantly streams 8‑bit unsigned PCM data to mix directly into the output waveform
    • 1 sine wave LFO (low frequency oscillator) channel
    • Mapped to the Z80 address space — 68000 must request the Z80 bus to use
    • Some Mega Drive 2 systems actually use the core from the chip's CMOS equivalent, the YM3438
    • IRQ interrupt capabilities: IRQ2 sound interrupt [7]
  • PSG sound chip: Sega PSG (SN76496)[8], clocked at the Z80 clock speed (3.58 MHz in NTSC, 3.55 MHz in PAL) and built into the VDP — same as with the Master System
    • Based on TI SN76489
    • 4 audio channels: Three channels of pure square wave tones, and one noise channel
      • The noise channel can play either white noise or "periodic noise" either at one of three preset frequencies or using the frequency of the third tone channel (consequently, that channel will be mute)
    • Can be freely accessed by both the 68000 through the VDP and the Z80 through its memory map
  • The cartridge connector has two pins which allow stereo sound mixing directly from cart. No game used this, however, but the 32X uses it for its PWM audio
  • The Mega Drive 1 has mono audio output from the TV output and stereo output from a built‑in headphone jack, plus a built‑in volume control. Future models drop the headphone jack and do stereo output from the TV output

Graphics

  • GPU chipset:
    • VDP: Sega 315‑5313 (Yamaha YM7101) [1][9]
      • Based on Sega Master System VDP (in turn, based on TI TMS9918)
      • All TMS9918 modes were removed and replaced with several new modes
      • Controls background playfields and foreground sprites [10]
      • Clock rate: 13.3 MHz
      • Pixel clock rate: 6.711648 MHz [11]
      • Bus width: 16‑bit
      • Memory bus clock rate: 6.711648 MHz
      • IRQ interrupt capabilities: IRQ6 VBlank interrupt, IRQ4 H‑Int (Horizontal Interrupt) scanline interrupt [7]
    • DMA controller: Capable of DMA, high-speed fills and memory transfers, can transfer data from 68000 address space to VRAM/CRAM/VSRAM during active display and VBlank [12]
    • RGB/Composite Video Encoder: Sony CXA1145 (NTSC/PAL)[1][13] / Fujitsu MB3514 (PAL) [9][14]
      • Colorburst clock frequency: 3.579545 MHz (NTSC), 4.433618 MHz (PAL) [15]
  • Screen resolutions:
    • Progressive scan resolutions:
      • NTSC: 320×224, 256×224
      • PAL: 320×224, 256×224, 320×240, 256×240
    • Interlaced resolutions:
      • NTSC: 320×448, 256×448
      • PAL: 320×448, 256×448, 320×480, 256×480
      • "Interlaced mode" doubles the height of all four; it was used by some games, such as Sonic 2 for two‑player mode.
  • Scanlines:
    • Progressive scan: 262 (NTSC), 312 (PAL) [16]
    • Interlaced: 524 (NTSC), 624 (PAL)
  • Refresh rate: 59.92274 Hz (NTSC), 50.31974 Hz (PAL)
    • Frame rate: 59.92274 frames/sec (NTSC), 50.31974 frames/sec (PAL)
  • Four graphics layers: two tile planes (just a grid of tiles), "window" tile plane (cannot be transparent), sprite plane
    • Tilemap background planes: 2 parallax scrolling planes, with line and row scroll effects per plane (can scroll and overlap rows of tiles)[17], vertical and horizontal line scrolling[18], column scrolling (2 tiles per column), horizontal and vertical tile flipping, 1800 tiles per frame [6]
    • Background window plane, behind scrolling planes [18]
    • Sprite plane: 80 sprites on screen, 20 sprites per scanline, 16 sprite sizes (8×8 to 32×32 pixels),[6] 16 colors per sprite,[19] integer sprite zooming [20] (up to 320x224),[18] definable sprite priorities, 32 bytes per sprite,[10] sprite flipping, virtual 512×512 sprite space [21]
    • Note: Priorities can be defined between planes. [10]
  • Colors on screen: [22][17]
    • Standard: 64 colors
    • Mid‑frame palette swap: 75 colors
    • Shadow/Highlight mode: 183–192 colors
    • Direct color (homebrew) mode: 512 colors (160×224 resolution)
    • Color can be changed for each line [18]
    • 16 colors (4‑bit) per pixel [12]
  • Color palette: [22]
    • Standard: 512 colors
    • Shadow/Highlight mode: 1536 colors
  • Shadow/Highlight mode: Hardware lighting,[22] shadow generation (matching each character's shape),[18] triples color palette and colors on screen, increases colors per tile
  • Video RAM: 65.1875 KB (66,752 bytes)
    • 64 KB internal VRAM — used to store graphics tiles, mappings for all layers, and horizontal scrolling
    • 64 9‑bit words of internal CRAM — used to store the color palette
      • 64 colors split into four 16‑color lines; each tile can be drawn with one of these four color lines
      • The first color in each line is transparent and any color of the entire palette can be used as a "background color" (when no pixels are drawn at a location); consequently the Mega Drive can display 61 colors on screen at once (unless raster effects or the Shadow/Highlight modes are used, in which case this number increases depending on the extent used)
      • Colors are 9‑bit RGB with 3 bits per color component, allowing for 512 colors
      • Shadow/Highlight modes increase color gamut
    • 80 bytes internal VSRAM — used for vertical scrolling (10‑bit words, up to 20 different vertical scroll values for each of the two scrolling playfields)[6]
  • VDP fillrate: 13.3 MPixels/s
    • Pixels per frame: 221,952 (NTSC), 264,309 (PAL)
    • Sprite fillrate: 320 sprite texels per scanline, 81,920 texels (80× 32×32 sprites) per frame,[22] 4.908 MTexels/s (NTSC), 4.122 MTexels/s (PAL)
  • VDP pixel bandwidth: 6.341934 MB/s (4‑bit per pixel)
    • Pixel bandwidth per frame: 103.354 KB (NTSC), 123.078 KB (PAL)
  • DMA transfer rate: 864.754 KB/s (NTSC), 1355.782 KB/s (PAL) [23]
    • DMA transfer per frame: 14,777.5 bytes (NTSC), 27,590 bytes (PAL)
    • Note: The term "Blast Processing" primarily referred to the fast DMA transfer rate.
  • 3D polygons: Capable of rendering 3D polygons with stock hardware (without enhancement chips)
  • Other features: Semi‑transparency, FIFO memory circuit design, read/write of one line buffer method for drawing [18]

Memory

  • System RAM: 136 KB
    • Main RAM: 64 KB (repeated over the upper 2 MB of address space)
    • VRAM: 64 KB
    • Audio RAM: 8 KB
  • VDP internal RAM: 152 bytes [21]
    • CRAM (Color RAM): 72 bytes (576 bits)
    • VSRAM (Vertical Scrolling RAM): 80 bytes (640 bits)
  • Cartridge memory: 512–5152 KB
Configuration
  • System memory buses: [1]
    • 16‑bit system bus — 68000 & VDP <‑> Main RAM & Cartridge ROM/RAM
    • 8‑bit system bus — Z80 & YM2612 <‑> Audio RAM
    • 16‑bit video bus — VDP <‑> VRAM
Bandwidth
  • Internal processor bandwidth:
    • 68000 internal bus: 14.630317 MB/s (NTSC), 14.514923 MB/s (PAL)
    • Z80 internal bus: 3.414154 MB/s (NTSC), 3.385543 MB/s (PAL)
    • VDP internal CRAM/VSRAM: 12.801452 MB/s
  • System RAM bandwidth: 25.73 MB/s
    • Main RAM: 10.038675 MB/s
    • VRAM: 12.801452 MB/s
    • Audio RAM: 2.889922 MB/s
  • Cartridge ROM bandwidth: 9.536743 MB/s (most cartridges), 14 MB/s (some cartridges)

Memory map

Mega Drive Memory Map
Start End Size Description
$000000 $3FFFFF $400000 ROM Cartridge
$400000 $7FFFFF $400000 Expansion Port Area (used by the Sega CD)
$800000 $9FFFFF $200000 Unallocated (used by the Sega 32X)
$A00000 $A0FFFF $10000 Z80 Memory
$A10000 $A10FFF only various meaningful System registers
$A11000 $A11FFF only $A11100 and $A11200 meaningful Z80 control (/BUSREQ and /RESET lines)
$A12000 $AFFFFF only several meaningful Assorted registers
$B00000 $BFFFFF $100000 Unallocated
$C00000 $DFFFFF $1F; mirrored VDP
$E00000 $FFFFFF $10000; mirrored Work RAM (games usually only use the uppermost mirror, at $FF0000)

Input

  • Controller input: Two male DE‑9 controller ports; one female DE‑9 expansion port (early MD1s only)
    • Controller ports support two modes: parallel and serial
    • Parallel supports 7‑bit bidirectional, with the console setting the direction of each bit.
    • Parallel also supports optional active‑low interrupts on the TH line. (mapped to 68000 IRQ 2)
    • Serial mode supports up to 4800 bps. (used by the Mega Modem on port 3)
  • Expansion port: Used for Sega CD.
    • Provides access to /FDC ($A120xx) and /DISK to indicate Sega CD presence.
    • Maps Sega CD PRG RAM to $000000 when no cartridge is present, $400000 otherwise.

Upgrades

Sega Virtua Processor

See Sega Virtua Processor specifications.

The Sega Virtua Processor (SVP) enhancement chip used in the Virtua Racing (1994) cartridge adds the following specifications:

  • GPU: Samsung SSP1601 DSP @ 23 MHz (25 MIPS)
  • 3D polygon graphics: 9000 polygons/sec
  • Audio: 2 PWM channels
  • RAM: 131 KB (2 KB instruction cache, 1 KB SRAM cache, 128 KB FPM DRAM)

Sega CD

See Sega Mega-CD technical specifications.

The Sega CD (Mega CD) add‑on, released in 1991, adds the following specifications:

  • CPU: Motorola 68000 @ 12.5 MHz (2.19 MIPS)
  • GPU: Sega ASIC coprocessor
  • Sound chip: Ricoh RF5c164
  • Graphics: Sprite/tilemap scaling and rotation
    • Colors on screen: 128 colors (HAM), 256 colors (FMV)
    • 3D polygon graphics: 960 polygons/sec
  • Sound: 8 PCM channels (16‑bit, 32 kHz), 1 streaming CD‑DA channel (16‑bit, 44.1 kHz)
  • RAM: 848 KB (768 KB main, 64 KB audio, 16 KB cache)

Sega 32X

See Sega 32X technical specifications.

The Sega 32X add‑on, released in 1994, adds the following specifications:

History

Main article: History of the Sega Mega Drive.

Games

Main article: List of Mega Drive games.

Launch titles

A Japanese Sega Mega Drive (Model 1) overloaded with add-ons including the Sega Mega-CD (Model 1), Sega 32X, Remote Arcade System and Mega-CD Karaoke.

Japan

North America

Europe

Magazine articles

Main article: Sega Mega Drive/Magazine articles.

Promotional material

Print advertisements

Pamphlets

Television advertisements

Artwork

References

  1. 1.0 1.1 1.2 1.3 File:Sega Service Manual - Genesis II - Mega Drive II (PAL) - 001 - June 1993.pdf
  2. https://github.com/ekeeke/Genesis-Plus-GX/blob/master/core/system.h
  3. http://www.digitpress.com/faq/megadrive.htm
  4. Obsolete Microprocessors
  5. FM-Drive User Manual
  6. 6.0 6.1 6.2 6.3 File:GenesisTechnicalOverview.pdf
  7. 7.0 7.1 Genesis (MESS)
  8. SN76496 (MAME)
  9. 9.0 9.1 9.2 Mega Drive PCB revisions
  10. 10.0 10.1 10.2 File:GenesisTechnicalOverview.pdf, page 2
  11. https://pineight.com/mw/index.php?title=Dot_clock_rates
  12. 12.0 12.1 File:GenesisTechnicalOverview.pdf, page 3
  13. File:CXA1145P datasheet.pdf
  14. File:MB3514 datasheet.pdf
  15. 315-5313 Information
  16. File:GenesisTechnicalOverview.pdf, page 14
  17. 17.0 17.1 Sega Genesis Comparison
  18. 18.0 18.1 18.2 18.3 18.4 18.5 How Sega Built the Genesis: Masami Ishikawa Inteview
  19. Sega Programming FAQ (October 18, 1995) (Wayback Machine: 2001-01-14 21:14)
  20. Sega Master System VDP Documentation
  21. 21.0 21.1 Sega Genesis VDP Documentation
  22. 22.0 22.1 22.2 22.3 Sega Genesis VDP Documentation
  23. File:GenesisTechnicalOverview.pdf, page 45
  24. http://emu-docs.org/Genesis/ssf2.txt
  25. htt (Wayback Machine: 2009-02-04 19:02)
  26. 26.0 26.1 Second Dimension R&T DxS-GEN24STH-01
  27. File:HM65256B datasheet.pdf
  28. File:TC51832 datasheet.pdf
  29. File:HM53461 datasheet.pdf
  30. File:KM424C64 datasheet.pdf
  31. File:MB81461 datasheet.pdf
  32. File:TMM2063P datasheet.pdf
  33. File:UPD4168 datasheet.pdf
  34. File:KM6264B datasheet.pdf
  35. File:LC3664R datasheet.pdf
  36. ROM Part Numbers
  37. File:MB834200A datasheet.pdf
  38. 38.0 38.1 File:MB838200B datasheet.pdf
  39. File:M27C322 datasheet.pdf


Sega Mega Drive
Topics Technical specifications (Hardware comparison) | History | List of games | Magazine articles | Promotional material | Merchandise | Cartridges | TradeMark Security System
Hardware Japan | North America | Western Europe | Eastern Europe | South America | Asia | South Korea | Australasia | Africa
EZ Games | LaserActive | Mega Jet | Mega PC | Mega Play | Mega-Tech System | Nomad | Teradrive | Mega Drive Mini | Mega Drive Mini 2
New Mega Drive | Tianli VCD/DVD Players | "Consoles on a chip" | Licensed clones (Magic 2 | Mega Game II | Power Pegasus | Super Bitman)
Unlicensed clones
Add-ons Game Box | Power Base Converter | Mega-CD | 32X (Mega-CD 32X) | Mega Modem | Demo System DS-16
Cases Sega Genesis Nomad Carrying Case | System Carry Case
Controllers Control Pad | Six Button Control Pad | 6 Button Arcade Pad | Arcade Power Stick 6B | Konami Justifier | MK-1470
Action Chair | Activator | Arcade Power Stick | Keyboard | MegaFire | Mouse | Mega Stick | Menacer | Remote Arcade System | Ten Key Pad | Third Party Controllers
Accessories 4 Way Play | Cleaning System | Control Pad Extension Cord | Genesis Speakers | Headset | HeartBeat Catalyst | Microphone | Region converter cartridges | Mega Terminal | Nomad PowerBack | RF Unit (Mega Drive 2) | SCART Cable (Mega Drive 2) | Stereo Audio Video Cable | Team Player | Video Monitor Cable | Third Party Accessories
Network services Sega Channel | Sega Game Toshokan | Mega Anser | Mega Net | TeleBradesco Residência | XB∀ND
Development tools ERX 308P | ERX 318P | Sprobe | SNASM68K | SNASM2 (Mega Drive) | SNASM2 (32X) | PSY-Q Development System (Mega Drive) | PSY-Q Development System (32X) | 32X CartDev | Sega Mars Development Aid System | Sega 32X Development Target
Unreleased Edge 16 | Floppy Disk Drive | Mega Play 1010 | Sega VR | Teleplay System | Video Jukebox
Sega Home Video Game Systems
83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11
SG-1000 SG-1000 II Mega Drive Mega Drive II
SC-3000 Mega-CD Mega-CD II Genesis 3
Sega Mark III 32X Dreamcast
Master System Master System II
AI Computer Game Gear
Saturn
Pico Beena