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The Mega Drive (メガドライブ Mega Doraibu), also known as the Sega Genesis in North America, was Sega's third console.

It was Sega's most successful console, selling over 30 million units worldwide, including more than 20 million in the United States, 8 million in Europe, 3.58 million in Japan, and 3 million in Brazil. Its rival was the SNES. The Mega Drive / Genesis outsold the SNES in Europe and Brazil, however the SNES outsold the Mega Drive in Japan, North America and Spanish America.



Although the Sega Master System had proven a success in Brazil and Europe, it failed to ignite much interest in the Japanese or North American markets, which by the mid-to-late 1980s were both dominated by Nintendo with 95% and 92% market shares respectively. Hoping to dramatically increase their share, Sega set about creating a new machine that would be at least as powerful as the then most impressive hardware on the market - the 16-bit Commodore Amiga, Atari ST and the Macintosh II home computers.

The first name Sega considered for their console was the MK-1601, but they ultimately decided to call it the "Mega Drive". "Mega" had the connotation of superiority, and "Drive" had the connotation of speed and power. Sega used the name Mega Drive for the Japanese, European, Asian, Australian and Brazilian versions of the console. The North American version went by the name "Genesis" (a.k.a Sega Genesis) due to a trademark dispute, while the South Korean versions were called Super GameBoy (수퍼겜보이) and Super Aladdin Boy (transliterated from 수퍼알라딘보이; this was the Korean version of Mega Drive 2).

The Korean-market consoles were licensed and distributed by Samsung Electronics. Since the Sega Saturn was on the way, the Sega Genesis got 2 Add-ons for life support to last long enought to bring the Saturn on the scene. One of these add-ons was the Sega 32X, a 32-bit add-on compatable with 16 and 32-bit games. The other one was the Mega-CD. (a.k.a Sega CD)

Japanese release[]

The Mega Drive was released in Japan in October 29 1988 for ¥21,000, almost exactly a year after the first of the fourth generation consoles NEC's PC Engine. Although this initially caused slow sales, the Mega Drive soon eclipsed the earlier machine in popularity. However, after the release of the PC Engine CD add-on and the Nintendo Super Family Computer, the Mega Drive soon lost ground. The Mega Drive was not as popular as the two aforementioned systems in Japan.

North American release[]

In 1987, Sega announced a North American release date for the system of January 9 1989, making it the second console to feature a 16-bit CPU (the first one being the Mattel Intellivision) and the first to feature single-instruction 32-bit arithmetic. Sega was not able to meet the initial release date and U.S. sales began on August 14, 1989 in New York City and Los Angeles with a suggested retail price of USD $200 at launch. The Mega Drive was released in the rest of North America on September 15 of the same year with the price reduced slightly to $190.

The Mega Drive initially competed against the 8-bit Nintendo Entertaiment System (NES), over which it had superior graphics and sound. Nonetheless, it had a hard time overcoming Nintendo's ubiquitous presence in the consumer's home and the huge catalogue of popular games already available for it. In an attempt to build themselves a significant consumer base, Sega decided to focus on slightly older buyers, especially young men in their late teens and early 20s who would have more disposable income and who were anxious for more "grown-up" titles with more mature content and/or more in-depth gameplay.

As such, Sega released titles such as Altered Beast and the Phantasy Star games. Although the NES and Nintendo's impending SNES were still threats to Sega's market share, they had forced the theoretically competitive TurboGrafx-16 system into relative obscurity, thanks in part to NEC's poor North American marketing campaign.

European release[]

The European release was on November 30, 1990. In the United Kingdom and the Republic of Ireland, it was priced at £189.99 / €189.99. The first UK shipment of 30,000 units was sold at retailers Comet, Dixons, Rumbelows and Toys R Us.

Brazilian release[]

The Mega Drive was released by Tec Toy in 1990, only a year after the Brazilian release of the Sega Master System. Tec Toy also released the internet service Mega Net, and made exclusive games including a port of Duke Nukem 3D. The Mega Drive is still manufactured in Brazil, with many games built into the console.


In 2012, ATGames released the Firecore Sega Mega Drive 20-in-one system. It was made as the "Model 4" Mega Drive, and included 20 built-in games, as well as a switch that switches the adapters inside the cartridge slot to play PAL and NTSC games. Soon after, ATGames re-released their Firecore model in America as a Plug'N'Play console, though the name of a Plug'N'Play console does not fit it's technical specifications, as it maintains the majority of it's Japanese counterpart.

However, there are differences. This time, the Classic Game Console included 40 SEGA games, as well as 40 arcade games. This combined added up to 80 built in games. The console no longer donned the PAL/NTSC switch, so it is incompatible with PAL games. Instead of wired six-button controller adaptions, the American Firecore sported two infra-red wireless six-button controllers, though the Nine Pegs were still available for use.


Eventually, the main competition for the Mega Drive became Nintendo's 16-bit SNES, over which it had a head start in terms of user base and number of games, reversing the problem Sega had faced against the NES. The Mega Drive continued to hold on to a healthy fan base composed significantly of RPG and sports games fans. The release of Sonic the Hedgehog in 1991 threatened Nintendo's up-to-then stranglehold on the number one console position in the USA. Sonic was released to replace former mascot Alex Kidd, and to provide the "killer app" that Sega needed. This sparked what was arguably the greatest console war in video gaming history. By 1992, when Sonic the Hedgehog 2 released, Sega had become the market leader.

The NEC TurboGrafx-16 (PC Engine) was also a competitor to the Mega Drive, but it did not have a major hold on the 16 bit era outside of Japan. The other main competitor, the Neo Geo AES from SNK, did not sell well due its large price tag both for the system itself and for its titles.

By 1992, Sega was enjoying a strong hold on the market, holding a 55% market share in North America. Faced with a slight recession in sales and a brief loss of market share to the SNES, Sega again looked to Sonic to rejuvenate sales. The release of the highly anticipated Sonic the Hedgehog 2, coinciding with an aggressive ad campaign that took shots at Nintendo, fueled Mega Drive sales a while longer and boosted Sega's market share percentage back up to an astounding 65%.

Less than a year later, in 1993, Sega released a redesigned version of the console at a newly reduced price. By consolidating the internal chipset onto a smaller, unified motherboard, Sega was able to both physically reduce the system's size and bring down production costs by simplifying the assembly procedure and reducing the number of integrated circuits required for each unit.

Aside from the release of the Mega-CD and Sega 32X add-ons for the Mega Drive, Sega's last big announcement came in the form of a partnership with Time Warner in the U.S. to offer a subscription-based service called Sega Channel, which would allow subscribers to "download" games on a month-by-month basis. This became the foundation for the concept of digital distribution, which would start with the release of by Blizzard in 1996.

The failures of the Mega CD and 32X, a lack of effective advertising, Nintendo’s SNES and disputes between Sega of America and Sega of Japan had taken their toll on the company. By mid-1994, Sega's market share had dropped from 65% to 46%, and the official announcements of newer, more powerful consoles, such as the Sega Saturn, the Sony Playstation and the Nintendo 64 signalled that the 16-bit era was drawing to a close. Interest in the Mega Drive suffered greatly as a result, compounding its already falling sales. In 1997, less than two years after the debut of their Saturn console, Sega quickly brought their participation in the 16-bit era to an end by discontinuing production of the Mega Drive and its associated accessories. Third-party production and development continued, and still does to the present-day.

This decision by SEGA infuriated consumers around the world who had bought the Sega Mega CD and 32X attachments only to see Sega abandon all support. This can, at least in slight, be seen as a contributing factor to the downfall of Sega as a console manufacturer. The console wasn't discontinued in Europe, Austrailia and New Zealand until 1998, where it was outsold by the Super NES as well as the Saturn. The Mega Drive / Genesis was pulled out of the Japanese and North American markets before the SNES; however, this is not including the licensed Majesco and ATGames versions of the Mega Drive.

According to the revised NPD's North American market data published from 2014, the SNES ultimately outsold the Genesis in the US market [1], as well as in Asia, Oceania and Spanish America. The Mega Drive defeated the SNES in Europe and in Brazil.

The Mega Drive / Genesis sold over 30 million units worldwide. This was less than the 49 million sold by the SNES worldwide, according to Nintendo. The higher overall worldwide sales of the SNES is also due to the wide lead it had over the Mega Drive in Japan and the US markets.

Resurgent popularity[]

In recent years, there has been something of a revival of interest in the Mega Drive, led largely by the grey market trade in both unlicensed cartridges and dumped ROMs, which are played through emulators such as Kega Fusion, GENS, or Genecyst. There is also a trend towards home programming, using the PC-based SGCC.

In the 2000s, a trend emerged based around plug-and-play TV games, and Radica has released licensed, self-contained versions of the Sega Mega Drive in North America (as the Play TV Legends Sega Genesis) which contain six popular games in a small box and control pad. It does not have a cartridge slot, and thus is a dedicated console. However, Benjamin Heckendorn, of Atari portablizing fame, has proven that it is possible to connect a cartridge slot with some soldering.

The GameTap subscription gaming service includes a Mega Drive emulator, and has several dozen licensed Mega Drive games in its catalogue.

On March 23, 2006, it was announced at the Game Developers Conference in San Jose, California that Nintendo will offer Sega Mega Drive games to be emulated on the Wii home console. These games will be available along with other systems titles under the Wii's Virtual Console. The 16-bit Sega selections available on the Virtual Console at launch are Altered Beast, Columns, Dr. Robotnik's Mean Bean Machine, Ecco the Dolphin, Golden Axe, Gunstar Heroes, Ristar, and Sonic the Hedgehog. Each title costs 800 Wii Points ($8US) except in Japan, where they are 600 Points (¥600).

On May 22, 2006 Super Fighter Team released Beggar Prince, a game translated from a 1996 Chinese original. It was the first serious commercial Mega Drive game since 1998 and was released worldwide.

At Tokyo Game Show on September 21, 2006, Ken Kutaragi, President and CEO of Sony Computer Entertainment, announced that Sega Mega Drive game ports will be available on the PlayStation Network Platform (network service for the PlayStation 3). No specific titles or price points have been confirmed as of yet, with Kutagari simply stating that these specifics will be discussed with individual publishers. This, however, was later contradicted by SEGA Japan when a short statement was issued stating "that such claims are not correct at this point".


During its lifespan, the Mega Drive quite possibly received more officially licensed variations than any other console. While only one major design revision of the console was created during its lifespan, each region has its own peculiarities and unique items, while other variations were exercises in reducing costs (such as the removal of the little-used 9-pin EXT. port) or expanding the capabilities of the Mega Drive

The most notable reincarnations were that of Majesco and AtGames. Majesco took the larger step, as they were bold and named it the Mega Drive Model 3. It lacked any feature the first two models had besides the ability to play Mega Drive cartridges. Later, in 2011, the famed retro-revival company AtGames responded to Retrons's descision to reboot the SNES and NES by resuscitating their former rival, now renamed to the AtGames Firecore Sega Mega Drive Classic Game Console.

It boasts higher tech controllers (as they are wireless) and comes bundled with 80 built-in games. It could play Mega Drive cartridges as long as they were in reasonable condition, as well as the Power Base Converter. However, this model has gottan complaints for its inaccuracy of sound, as the new model does not have a dedicated FM synthesis chip. Instead it relies on hardware emulation which often chooses the wrong sound or an incorrect tone. Some games may even produce static instead of music or sound effects.  

Full technical specifications[]

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Hardware specifications

Motorola 68000 (or equivalent)

  • Runs at 7.61 MHz in PAL consoles, 7.67 MHz in NTSC consoles.
  • Some systems contained clones of the Motorola 68000 manufactured by Hitachi and Signetics.
  • Signetics 68K only found in early revisions as this CPU is known to be inefficient.
Secondary processor

Zilog Z80 (or equivalent)

  • Runs at 3.55 MHz in PAL consoles, 3.58 MHz in NTSC consoles
  • Used as main CPU in Master System compatibility mode.


Memory specifications
Boot ROM
  • 2 KB
  • Known as the "Trademark Security System" (TMSS)
  • When console is started, it checks the game for certain code given to licensed developers
  • Unlicensed games without the code are thus locked out
  • If a game is properly licensed, the ROM will display "Produced by or under license from Sega Enterprises Ltd."
  • Boot ROM is not present on earlier versions of the Mega Drive and Genesis
  • Some earlier games not designed for the TMSS may not work in later consoles
Main RAM
  • 64 KBytes
  • Part of M68000 address space
Video RAM
  • 64 KBytes
  • Cannot be accessed directly by CPU, must be read and written via VDP (Video Display Processor - see below)
Secondary RAM
  • 8 KBytes
  • Part of Z80 address space
  • Used as main RAM in Master System compatibility mode
Audio RAM
  • 8 KBytes
Cartridge memory area (ROM space)
  • Up to 4 MBytes (32 Megabits)
  • Part of M68000 address space
  • Game cartridges larger than 4 MBytes must use bank switching


The Genesis 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. It contains both mode 4 (for Master System compatibility) and mode 5 (for native Genesis games). However, Master System programs can switch the VDP into mode 5 and make use of advanced VDP features. This page only discusses mode 5 capabilities.

Graphics Processing specifications

4 (2 scrolling playfields, 1 sprite plane, 1 'window' plane), per-tile priority

Sprites: Up to 80 on-screen 320x240 or 320x480 pixel mode or 64 256x240 pixel mode.
Palette: 512 colors (1536 using shadow/highlight mode)
On-screen colors: 64 × 9-bit words of color RAM, 4 lines of 15 colors plus transparent, allowing 61 on-screen colors (up to 183 via raster effects and shadow/highlight)
Screen resolution
  • 256x224 (32Hx28V), 320x224 (40Hx28V), 256x240 (32Hx30V, PAL only), 320x240 (40Hx30V, PAL only)
  • Interlace mode 1 provides no increase in resolution, but still generates a true interlaced signal
  • Interlace mode 2 can provide double the vertical resolution (i.e. 320×448 for NTSC, 320x480 for PAL). Used in Sonic 2 for two-player split screen
Scroll size

Width and height independently set to 32, 64, or 128 cells as VRAM allows


Sound Processing specifications
Main sound chip

Yamaha YM2612

  • Six FM channels, four operators each; channel 6 can be used for CM data or as a regular channel
  • Programmable Low frequency oscillation|low-frequency oscillator and stereo panning
  • Runs at 7.6 MHz
Secondary sound chip

Texas Instruments SN76489 compatible device built into VDP.

  • Four-channel PSG (Programmable Sound Generator)
  • Three square wave channels, one white noise channel
  • Programmable tone/noise and attenuation
  • Used for Master System compatibility mode as well as to supplement FM
  • Different random noise generation compared to a real SN76489/SN76489A chip

Inputs and outputs[]

Input and output list
RF output

RCA jack connects to TV antenna input

  • Exists on original model European, Brazilian and Asian Mega Drive and North American Genesis only
  • Other models must use external RF modulator which plugs into A/V output
A/V output

DIN connector with composite video, RGB video, and audio outputs

  • Mega Drive and the first model Genesis have an 8-pin DIN socket (same as Sega Master System) which supports mono audio only
  • Mega Drive 2, Multimega, and other models have a 9-pin mini DIN socket with both mono and stereo audio
Power input
  • Positive tip barrel connector.
  • Requires 9-10 volts DC, 0.85-1.2 A depending on model.
Headphone output

Amplified 3.5-mm stereo jack on front of console with volume control

  • Exists only on original model Mega Drive and Genesis units
  • Provides stereo audio on models which have the mono 8-pin DIN A/V output
  • Also suitable for passive speakers
  • must be used for mixing audio to the Sega CD
"EXT" port

DE-9F (9-pin female D-connector) on back of console

  • Used with the Meganet modem peripheral, released only in Japan
  • Exists on all first-model Japanese Mega Drive units, and on early American Genesis and PAL (European, Australasian and Asian) Mega Drive units
  • May have been used for game selection on arcade adaptations of the Mega Drive console
Control pad inputs

Two DE-9M (9-pin male D-connectors) on front of console

Expansion port

Edge connector on bottom right hand side of console

  • used almost exclusively for Sega Mega-CD connection
  • not present on Genesis 3 model
  • also used for the Sega Genesis 6 Cart Demo Unit (DS-16) in stores.

Master System compatibility[]

One of the key design features of the console was its backwards compatibility with Sega's previous console, the Sega Master System (SMS). The 16-bit design was based upon the 8-bit design, albeit enhanced and extended in many areas. In order to achieve backwards compatibility, the original SMS central processor and sound chip (the Z80 and SN76489) were included in the Genesis and the Genesis's Video Display Processor (VDP) was capable of the SMS VDP's mode 4 (though it cannot run in modes 0, 1, 2, or 3).

As the cartridge slot was of a different shape, Sega released the Power Base Converter, a separate device that sat between an SMS cartridge and the Genesis's cartridge slot. The Power Base Converter did not contain any SMS components, instead functioning as a pass-through device. The converter contained a top slot for cartridge based games along with a front slot for card based games. Once an 8-bit game was inserted, the system put the Z80 in control, leaving the 68000 idle.

Both 2-button SMS pads and standard Genesis pads could be used to play SMS games, although due to slight differences in how the pads operate, some SMS games inadvertently cause the wrong set of inputs to be selected in a Genesis pad, preventing input from working properly and necessitating the use of an SMS controller. As with the SMS, the PAUSE button was not part of the gamepad connector and instead was implemented as a push-button switch on the device.

In Japan, the device was known as the Mega Adaptor. The PAL variant was called the Master System Converter in mainland Europe.

The Power Base Converter was not fully compatible with the redesigned Genesis 2, requiring the removal or modification of the device's casing to fit correctly due to the console's new shape. A second version, the Master System Converter II, was released to address this problem. This second version adapter, however, was produced in far fewer quantities and is much tougher to find (and more expensive) than the original Power Base Convertor.

Recently, a clone Power Base Converter fully compatible with both Model 1 and Model 2 Genesis / Megadrives was released by db Electronics. This particular variant fits inside a standard cartridge shell and does not suffer from casing issues like the original Power Base Converter.


  • Majesco's Genesis 3 (single-chip and dual-chip versions) retains the Mode 4 support but has the Master System compatibility removed from the bus controller logic. This renders the Power Base Converter or any other adapter useless. 68000 software can still disable and not use Mode 4.
  • One of the 68000's instructions, TAS, is intended for semaphore communication in multiprocessor machines and locks the 68000 bus during memory access. The Sega hardware did not support this unusual bus cycle and ignored the write-back phase. Two games, Gargoyles from Buena Vista Interactive, and Ex-Mutants from Sega make use of the TAS instructions and expect it not to write to memory. As a result, these games work on original Sega machines but not the Majesco Genesis 3, which has correct support for TAS.
  • It is not possible to overclock the Motorola 68000 CPU in some cases in excess of 300% (the current known world record is 25.4 MHz), though it may not be completely stable beyond a certain point on each console. The result of overclocking the CPU does speed up the games any, but actually doesn’t eliminates slowdown that some games are plagued by.
  • Another possible modification is to replace the stock 68000 processor with a 68010. Since the CPU isn't socketed, this requires the removal of the old CPU, and soldering in of the new. The 68010 is a pin-compatible enhanced version of the 68000, which is a bit more efficient internally and offers some new features. Also, the DAC's digital audio output may sound cleaner and less distorted because the 68010 has a "loop mode" to run small loops faster, which may allow the Z80 to receive PCM data faster. However, the 68010 is not 100% object code-compatible with the 68000, so machines modified with a 68010 processor are not able to run certain games properly, such as Sonic 3, Sonic and Knuckles, Street Fighter II, Red Zone, and a few others.
  • Contrary to popular belief, Model MK-1631 (Mega Drive 2) doesn’t have a Z80 CPU.
  • One of Sega's most famous advertisements in North American media was its slogan "Genesis does what Nintendon't", which showcased the graphics that the Genesis had against the NES.
  • By the time the SNES was released and Sonic the Hedgehog 2 as well, Sega promoted the console with Blast Processing, which was a term that Sega coined because the Mega Drive / Genesis's 68000 processor had a higher clock speed than the SNES's 65c816.
  • Later models of the system flashed the following text on the screen:
This is a fractured sentence that says "WELCOME TO THE NEXT LEVEL".
  • There is an extremely rare version of the console called the Mega Jet, which was originally available only for rent by JAL passengers, but later sold in small quantities.


See also[]


  1. Indirect Network Effects and the Product Cycle: Video Games in the U.S., 1994-2002, Matthew T. Clements (University of British Columbia & University of Texas) and Hiroshi Ohashi (University of Tokyo), February 2004 (NPD sales data)

External link[]

  • SegaBase - Comprehensive history of this system
  • Games - Cyborg Justice
This page uses content from Wikipedia. The original article was at Sega Mega Drive. The list of authors can be seen in the page history. As with Sega Wiki, the text of Wikipedia is available under the GNU Free Documentation License.

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