Sega Mega Drive

Sega Mega Drive
Manufacturer: Sega
Variants: Mega Drive 2, Genesis 3, Sega Mega Jet, Sega Nomad, Sega Teradrive
Add-ons: Sega CD, 32X, Power Base Converter, Super Magic Drive

The year 1987 found Sega in a curious position. The world was awash in 16-bit technology, and personal computers such as the Commodore Amiga and Atari ST were making large inroads on the 8-bit home videogame market. Sega's own 8-bit system, the Sega Master System (SMS), had not fared as well as had been hoped due to the dominance of the Nintendo Entertainment System (NES), but even that revered 8-bit console was losing out to these newer, high-end computers and their impressive array of videogames. Sega had already enjoyed considerable success with 16-bit arcade videogames such as Space Harrier and OutRun - it seemed like the ideal time had come to bring 16-bit technology to the home videogame console market, and Sega quickly decided to be the first to make the move. If 16-bit personal computers were being accepted so rapidly, they reasoned, then why not 16-bit videogame consoles? Nintendo, their chief competition, already had a 16-bit console in the design pipeline (the Super Famicom, aka the Super Nintendo), but they were in no hurry to market it. They were content to rest on the laurels of 8-bit sales, and thus left themselves wide open to the one-two marketing punch that Sega was about to pull.

Development

In the mid-to-late-1980s, Nintendo at the time had 95% of the North American market, and 92% of Japan's, and Sega's Master System was failing in North America and Japan. It is interesting to note that the opposite was true in European markets; as the Master System was released earlier than the NES due to Nintendo's horrendous licensing policies and distribution tactics (something one could argue continues to this day), the NES never enjoyed the popularity of the Master System did, particularly in Britain and France.

Since the System 16 arcade games that Sega were producing were popular worldwide, Hayao Nakayama, Sega's CEO at the time, decided their new home system would be a 16-bit one. The final design worked well and tied in with Sega's three new arcade boards produced alongside this new console; the MegaTech, MegaPlay, and the System C. Any arcade game made for these systems could easily, and thus rapidly, be made to work on the new console (a process known as porting). In this sense, the Mega Drive was one of, if not the first machines to truly bring the arcade experience home - a fact played up during their advertisements prior to the system's launch.

The first name Sega considered using for its 16-bit machine was "MK-1601", but later decided upon Sega Mega Drive[1]. The name was designed to imply superiority, speed, and power. However, "Mega Drive" was trademarked in the United States, so Sega chose the name Genesis for that region, a name meant to mark the beginning of a new age in videogames.

Release

In 1987, Sega announced their North American release date and stated that their own console was the first true 16-bit console (a dig at NEC's TurboGrafx-16, which was being marketed as 16-bit, despite being an 8-bit machine with a powerful graphics processor - a fact which is contended to this day).

Sega's new console was introduced to the Japanese market in November 1988 under the name Mega Drive (US$350).

The Genesis was released in the United States in January 9, 1989 in New York City and Los Angeles only. It sold for around $200 at launch and was to become Sega's most popular console. It was released in the rest of North America on September 15 at a reduced price of $190.

It made it to Europe and Brazil under the Japanese Mega Drive label (due to no such American copyright) in time for the 1990 Christmas period.

An initial criticism of the system was that there were too many shallow arcade ports in the Genesis' library - Michael Jackson's Moonwalker and Altered Beast being prime suspects - and that there was no killer app - however, powerful third party companies such as Electronic Arts (The Immortal), and Capcom (Strider) kept the console and software selling.

Even with these massively popular titles, Sega's system floundered for about two years against the popular NES in the States, until a Japanese game appeared in July 1991 about a feisty blue hedgehog created by artist Naoto Ohshima and developed by programmer Yuji Naka. Sonic was released to replace former mascot Alex Kidd (who had essentially been 'killed off' during the system's early life - see the 'Alex' and 'Stella' gravestones in Altered Beast's first level, for example), and to provide the killer app that was desperately needed to showcase the superior capabilities of Sega's console. The rest, as they say, is history. Nintendo had no choice but to rush the Super Nintendo (SNES) to the North American market due to the sudden and massive popularity of Sega's system and the veritable flood of sales that the new game had sparked. This started what was arguably the greatest console war in North American video gaming history, at least up until that point. By 1992, Sega had a 55% market share in the North American video game market.

July of 1992 saw the addition of the TradeMark Security System (TMSS) to newly-produced Mega Drive and Genesis systems. This altered the boot-up sequence in two important respects. First, it would not display the message "PRODUCED OR LICENSED BY SEGA ENTERPRISES" unless a specific string of microcode (SEGA) was found in the header of any cartridge plugged into the unit (referred to in development manuals as 'boot-up code'). This was in an attempt to prevent the production of unlicensed Genesis and MegaDrive games, and was the subject of a famous lawsuit between Sega and videogame vendor Accolade. The TMSS also checked the language and video output signals that the inserted cart required and would refuse to boot the cartridge unless they matched those that were hard-wired into the newer consoles. This was an attempt to prevent games made in one market from working in another, but enterprising users quickly discerned how to come up with various hardware hacks that bypassed this feature of the TMSS, and a similar conversion was later incorporated into newer cross-market cartridge adapters. However, it should not be assumed that, as early models of the Mega Drive and Genesis have no TMSS, that they are 'universal' - that is, region-free - the TMSS only prevented the game from running if it differed from the built-in 'English/Japanese' setting in the console. It is the software present in a cartridge that usually checks the frequency of the console's hardware video output (the 'PAL/NTSC' check), and will lock out based on this no matter what model of console it is running on. It is only at this period in the console's life that region lockouts became popular, due to importing becoming a fast-growing business - at one point after the Mega Drive's launch, one in five games sold in English gaming stores were imported. Another software check incorporated into most games was the checksum check, aimed at preventing unauthorized changes to game code or data.

Due to a lack of third-party support, especially once Nintendo unleashed the SNES to worldwide distribution, the Sega Genesis never became as successful as Nintendo's 16-bit console. Nevertheless, about 28.5 million consoles were sold worldwide during its lifetime, compared to about 48 million SNES consoles. It took a long time for Nintendo to eventually regain the number one spot on the market from Sega, and the only reason that the SNES finally overtook the Genesis in 1996 was that Sega's console was already declining in popularity. 32-bit videogame systems had been introduced in the last half of 1995 (the Sony PlayStation and the Sega Saturn), and suddenly 16-bit technology didn't look as appealing anymore. Nintendo, having decided to skip the 32-bit wave altogether, helped the underpowered SNES limp along via cartridges fitted with special enhancement chips, but Sega was not content to rest on its laurels. The Sega Genesis was allowed to slowly wither away, and was officially discontinued in all markets in 1998.

In retrospect, it was definitely no mistake to invest in Sega's 16-bit videogame console. Among the 1,031 titles that were released during its lifespan, which lasted about 10 years (1988 - 1998), are some excellent games that are unique to the system itself and many other evergreens that deserve to be played even today.

Types of Mega Drive Consoles

Standard Mega Drive

There were three main revisions of the standard Mega Drive console produced during the console's lifespan. Arranged in order of territorial release:

Japanese Sega Mega Drive 1

The model 1 console is a somewhat rectangular affair with an offset raised circle, originally released in 1988.

• Set internally as Japanese, 60Hz
• A/V out port (supports mono audio only)
• RF-Out port
• Headphone jack and volume control
• AUX Port (located beyond cartridge slot across from power and video connection)
• Supports Sega Mega-CD and Sega Super 32X
• Mechanial cartridge lock activates when power is turned on
• Gloss black finish
• On the circular molding is the text 'High Grade Multi Purpose Intelligent Terminal'. At the bottom of the circle, surrounding the power LED, is a purple square section.
• Cooling vents are located on the left-hand side.
• 'Sega Mega Drive' is printed in white on the lower right-hand side of the console.
• The reset button and start button on the joypad are blue.
• (All) Sega Mega Drive 1/Genesis models suffered from faulty RF Out ports and RF switches. Old Mega Drive 1 RF switches would have to be wriggled in the RF Out port to obtain a clear enough signal. The picture often had scanlines, ghosts and static onscreen.

American Genesis model 1

• Set internally as Overseas, 60Hz
• A/V out port (supports mono audio only)
• RF-Out port
• Cannot play Japanese Mega Drive games, due to shape of cartridge and console (though adaptaders were sold to bypass the cartridge slot shape).
• Headphone jack and volume control
• Cartridge lock removed
• EXT port
• Support for Sega CD and Sega 32X
• Larger "16-Bit" logo and a large "Genesis" logo is printed in front of cartridge port
• Reset button and Start button on Joypad are now cream-grey

European & Australian Sega Mega Drive model 1 (also released in New Zealand)

• Set internally as Overseas, 50Hz
• A/V out port (supports mono audio only)
• RF-Out port
• Cannot play Japanese Mega Drive games, due to shape of cartridge and console (though adapters were sold to bypass the cartridge slot shape).
• Cartridge lock removed
• AUX Port OR EXT Port
• The text 'High Definition Graphics·Stereo Sound' located behind cartridge port.
• The reset button and the start button are cream-grey.

Asian Sega Mega Drive model 1

This is a variant to the European Mega Drive 1, and is often mistaken for a Japanese Mega Drive 1.

• Set internally as Overseas, 50Hz
• A/V out port (supports mono audio only)
• RF-Out port
• No text printed around circle
• Larger '16-Bit' logo used
• 'Start' and 'Reset' button are blue
• Identical to European Mega Drive with NTSC Output

American Genesis model 2

The Genesis 2 console is the now-familiar square low-profile affair first released in 1993, with a streamlined case design and no headphone jack. This was the first version of the console to have the TMSS system built-in from the start, breaking compatability with a tiny number of early releases (due to the lack of the 'SEGA' text in the ROM header - particularly early Codemasters releases). Due to its changed footprint, a new version of the Sega CD, the Sega CD 2, was made to accommodate this. It should also be noted that this model of the console was released almost simultaneously worldwide, and remained in production until 1998. Features include:

• A/V port is now one custom multi-out port for picture and sound. This port had stereo sound capability built-in, unlike the model 1 digital port's support for mono sound only - stereo sound coming from the headphone jack.
• RF-Out port removed
• Headphone jack removed
• Push-toggle power switch
• Unlike the Mega Drive 1/Genesis, the Genesis had a much better RF system that displayed a stronger and clearer signal.

Sega Mega Drive 2 in Japan

• RF-Out port removed in favour of A/V port
• Headphone jack removed
• Red Coloured flaps on cartridge port
• The text 'High Grade Multi Purpose Intelligent Terminal' located behind cartridge port.
• Packaged with 6-button controller as standard.
• Power LED removed
• Sliding power switch kept from model 1

Sega Mega Drive 2 in Europe

• RF-Out port removed in favour of A/V port
• Headphone jack removed
• Push-toggle power switch
• Auto-switching RF lead included

Other Variants

• Genesis 3
• X'eye (WonderMega)
• Sega CDX/ Sega Mega LD/ Multimega
• LaserActive
• MegaPlay
• Sega Nomad
• Sega Teradrive
• Aiwa Mega CD
• Play TV Legends

Specifications

CPU

• Main processor: 16-bit Motorola 68000 (or equivalent)
  • runs at 7.61MHz in PAL consoles, 7.67MHz in NTSC consoles
  • 16-bit data bus, 24-bit address bus
• Sub processor: 8-bit Zilog Z80a (or equivalent)
  • runs at 3.55MHz in PAL consoles, 3.58MHz in NTSC consoles
  • generally controls PSG (Programmable Sound Generator) & YM2612
  • 8 KBytes of dedicated RAM, often used for FM data and DAC samples
  • used as main CPU in Master System compatibility mode

Memory

• Boot ROM: 2 KBytes
  • runs when console is first switched on
  • contains 'copyright check' code for locking out unlicensed games
  • displays message 'Produced by or under license from Sega Enterprises Ltd.' when a licensed game is detected
  • Boot ROM is not present on earlier versions of the Mega Drive 1
  • The name Sega gave this boot ROM was the TMSS (TradeMark Security System)
• Main RAM: 64 KBytes
  • part of MC68000 address space
• Video RAM: 64 KBytes
  • cannot be accessed directly by CPU, must be read and written via VDP (Video Display Processor - see below)
• Sound RAM: 8 KBytes
  • part of Z80 address space
  • used as main RAM in Master System compatibility mode (the Z80 is the main processor present in the Master System)
• Cartridge memory area: up to 4 MBytes (32 Megabits)
  • part of MC68000 address space
  • Game cartridges larger than 4 MBytes must use bank switching
• ROM: 1 MBytes (8-MBIT)

Graphics

The Mega Drive has a dedicated VDP (Video Display Processor) for playfield and sprite control. This is an improved version of the Sega Master System VDP, which in turn is derived from the Texas Instruments TMS9918.

• Planes: 4 (2 scrolling playfields, 1 sprite plane, 1 'window' plane)
• Sprites: up to 80 onscreen, depending on display mode
• Palette: 512 colours
• Onscreen colours: 64 x 9-bit words of colour RAM, allowing 61 onscreen colours (up to 1536 using raster effects and Shadow/Highlight mode)
• Pixel resolution: depends on display mode
  • up to 320x240 (40x30 cells) for PAL
  • up to 320x224 (40x28 cells) for NTSC
  • interlaced modes can provide double the vertical resolution (i.e. 320x448 for NTSC). Used in Sonic 2 for 2-player split screen

Sound

• Main sound chip: Yamaha YM-2612 six-channel FM synthesiser chip
• Six FM channels, four operators each
• Programmable low-frequency oscillator and stereo panning
• Sixth optionally used for 8-bit digital audio
• Additional sound chip: Texas Instruments SN76489 4-channel PSG (Programmable Sound Generator)
  • PC format name: .GYM, .VGM
  • Sound RAM: 8 KBytes
  • 3 sound generators, 4 octaves each, 1 white noise generator

Inputs and outputs

• RF output: connects to TV aerial input
  • exists on European and Asian Mega Drive 1 only
  • other models must use external RF modulator which plugs into A/V output
• A/V output: DIN connector with composite video, RGB, and audio outputs
  • Mega Drive 1 has 8-pin socket (same as Master System), supports mono audio only
  • Mega Drive 2, Multimega, and other models have 9-pin mini DIN socket with both mono and stereo audio
• Power input: requires 9-10 volts DC, 0.85-1.2 A depending on model
• Headphone output: 3.5 mm stereo jack on front of console (Mega Drive 1 only)
• "EXT" port: 9-pin D socket for Meganet modem connection
  • exists on all Japanese and Asian Mega Drive 1 units, and on early European Mega Drive 1 units
• Control pad inputs: 2 x 9-pin D connectors on front of console
• Expansion port: Edge connector on bottom right hand side of console for Sega Mega-CD connection

Miscellaneous

• Signal/Noise Ratio: 56 db
• Storage medium: Cartridge
• The maximum size for any Genesis ROM is 4MB. However, back in 1991-1994, it cost a lot to manufacture even a 2MB ROM. This explains why the earlier games were so small, and, since music occupies a relatively large part of the ROM, why Sonic 1 and Sonic 2 only had 1 music per zone.
• The EXT port on the original Genesis/Mega Drive console is used with a modem peripheral that was only released in the Japanese market. The port operates identically to the two joystick ports, but has a female DB9 connector instead of a male DB9 one. The lines to this port also appear to have been used for game selection on arcade adaptations of the MegaDrive/Genesis hardware.
• The Stereo Headphone port on the front of the first model was either used for stereo headphones or speakers and/or used for mixing stereo sound for the Sega CD.
• The Expansion port most often used with the Sega CD was also used for the Sega Genesis 6 Cart Demo Unit in stores.
• Some emulation software can save game music to a format known as GYM. It works by recording the operation of the sound system to a destination file (the .gym file). The internal state of the emulator's sound chip code is sampled 60 times per second, and dumped to the file. While initially popular due to the lack of any serious competition the format does not offer a high fidelity reproduction of the original sound output, tends to produce very large files and was difficult to produce for PAL titles given the simplifications necessary for emulators at the time. The more-complete VGM format has now grown to replace it, which is capable of logging changes at up to 44100Hz, meaning that most sound may be accurately reproduced.

Input Devices

• Connectors: (2 DB-9 ports)
  • Standard 3-button gamepad
  • Enhanced 6-button gamepad
  • Sega Menacer lightgun
  • Sega Mega Mouse
  • Multitap (two different types are available)
  • Sega Activator
• Output Devices:
  • Separate R.F aerial and R.G.B outputs
  • (AUX connector - Genesis 1 only)
  • Stereo headphone jack (Original Model only)
  • 9 pin EXT port (Early original model only)

Hardware Add-ons

• Sega Mega Modem
• Sega CD (Expansion port on the bottom right hand side)
• Sega 32X
• XBAND
• Sega Mega Anser

Emulators for the Sega Mega Drive

Please see Comparison of Sega Mega Drive/Genesis Emulators for more information.

Miscellaneous

• Any game designed for either the Genesis or Mega Drive will work with its foreign counterparts (to a varying degree), but the unit will have to be set for the specific region the game was produced for (American 60Hz, European 50Hz or Japanese 60Hz). This involves a well-documented hardware modification to the unit in question. The Nomad will work with region-free releases, but suffers from the same incompatabilities as the Genesis model 2, as they share the same internal architecture. It is also possible to get past the region lock-out by using one of the following Action Replay or Game Genie codes. Which to use is dependant on the region of the console, but will let all games run on any system without a physical modification.
  • United States: Action Replay: 0001F0:5520 Game Genie: EAAT-BL1T
  • Europe: Action Replay: 0001F0:4520 Game Genie: EAAT-AL1T
  • Japan: Action Replay: 0001F0:4A20 Game Genie: EAAT-AY1T
• Contrary to popular belief, the model 2 console is not missing the Z80 chip - a belief born of the fact that the first official Master System converter released for the system (which was specifically shaped to fit the model 1) did not fit the different shape of the model 2 console's deck. Depending on the board revision, the model 2 system has either a Zilog Z84C00, a Custom Sega 315-5676 or similar. Since the Z80 is used for sound production by many games it is a necessary component. As also shown in the case of the official Master System Converter 2 and the third-party Datel Pro-MegaMaster (released only in Europe and Australia), the model 2 can in fact play Master System games perfectly well.
• Looking at the different regions of the world, the Mega Drive was most successful in the United States in its total sales. It was stronger in Europe for the sales-to-population ratio, however; the Mega Drive attained greater market penetration than the SNES in European markets - in particular Great Britain, which is famous for being the European Sega stronghold. By contrast, it never achieved popularity in Japan, which was 'Nintendo country'. Ironically, titles released in Japan are now the hardest to find for the system.
• One of the most interesting accessories to find nowadays is the once-popular Super Key from Action. This allowed you to play games on your own console regardless of intended market or console version. It also worked with the Sega CD and the CD-X, as well as the JVC X-Eye. Its popularity waned, however, after users learned how to modify their own consoles to be universal.
• Three announced Sega peripherals that were never released were the MegaPad (a graphics tablet along the lines of the venerable KoalaPad), the MegaKeyboard, and an external 3.5" floppy disk drive along the lines of the Nintendo unit for the NES. They were never released due to the poor market performance of the Mega Modem, also the reason why the Mega Modem (i.e. Telegames Modem as it was advertised in the States) was never released in any market other than Japan, the home of quirky peripherals. As for the MegaPad, it eventually evolved into the graphics pad used for the Sega Pico educational computer system.
• AM2's Arcade Racer analog steering wheel for the Sega Saturn was originally produced for use on the Mega Drive and 32X versions of Virtua Racing. It was advertised for the Genesis in the States but was never released due to high production costs.
• MSX was an attempt by several Japanese computer companies at setting a unified standard for personal computers, much in the same fashion that the IBM PC set the standard in American markets (which eventually supplanted MSX). At least two of the MSX-2 AX series computers (the AX-330 and the AX-990) included Mega Drive hardware and had a Mega Drive cartridge port near the top edge of the case. These were released in the Middle East by Universal (the Japanese vending company, not the movie studio). There is rumor that the AX-990 came with an unofficial 50-game multicart in Arabic of already available titles, but this has not been confirmed.

Special Thanks

• Sam Pettus (aka The Scribe's) Genesis Game List
• Hivebrain's Sonicology

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