After failing to make a real dent against the NESnote At least in North America and Japan; the Sega Master Systemdid well in Europe and South America, Sega decided just to top them. If Nintendo was dragging their feet to a 16-bit system (the arcade standard at the time), then Sega would beat them to the punch with a console based on its System 16 arcade board.
For the most part, it worked. This was helped by some of Nintendo's U.S. policies being ruled as anti-trust violations, by some developers supporting Sega due to them being a lot more lax note although Nintendo did later drop a lot of their remaining policies due to this, and their first truly successful hit known as Sonic The Hedgehog 1. So the Mega Drive was a hit, selling 35 million systems (with miniaturized versions and handhelds still on the market today.). There were also the Sega CD and 32X add-ons, but they were commercial flops.
Nintendo eventually had its own entry in the 16-bit era in the form of the Super Nintendo Entertainment System. The SNES and Mega Drive had a long and fierce console war that is probably the best-remembered of them all.
Known as the Genesis in North America ("Mega Drive" was already trademarked in the U.S. by someone making hard disk drives.)
Not to be confused with the band Genesis, the Web GameGe Ne Sis, the Genesis Device... or the book in The Bible.
The console had 16 bit hardware, which was prominently used as a marketing point over the 8-bit NES.
The system was heavily marketed for its ability to render objects faster than the SNES, a feature for which the Sega marketing division coined the term "Blast Processing". The higher performance allowed the Mega Drive to be able to render 3D polygons even without any special chips, like with Hard Drivin' and Star Cruiser.
Like the NES and SNES, the Mega Drive could expand through chips on the carts. One was the Sega Virtua Processor, which functioned like the Super FX chip on the SNES, allowing for more advanced polygonal rendering (it was in fact even more powerful than the Super FX chip). Unfortunately, incorporating it was a lot more expensive than a SNES chip, and only the port of Virtua Racing used it.
It also has a 2nd CPU, a Zilog Z80 running at 3.58 MHz, used for the Sound chips's CPU and Master System play back.
8 KB of extra RAM for backwards compatibility with the Sega Master System (although that requires an adapter).
Games ranged from 128KB (Columns, Ms. Pac-Man) to 5 MB (Super Street Fighter II). Keep in mind that these were advertised by their bit size, not their byte size, so they would be listed as 1 megabits to 40 megabits.
Up to 80 sprites on screen (not including background layer textures which could also appear animated), with a maximum of 20 sprites or 320 sprite pixels per scanline.
Two background layers in addition to the sprite layer.
Could not do scaling and rotating sprites, but the faster CPU could imitate them by resizing sprite data.
64 colors on screen (divided into four 16-color palettes), 512 total.
Yamaha YM2612 (OPN2)
Six concurrent FM channels (voices).
Four operators per channel.
Two interval timers.
Sixth channel can be used a software mixing channel for PCM
Texas Instruments SN76489
4 Analog generators.
3 squares one noise.
modded for stereo sound (the chip's standers can only do Mono)
Addons and peripherals
Power Base Converter: An add-on which allowed the Mega Drive to play Sega Master System games, either of the cartridge or the chip variety, and included support for the SMS's SegaScope 3D glasses. This was initially marketed for the first model Mega Drive, but a small quantity was made for the redesigned, compact Mega Drive (But only in Europe). Also, it can not play SG-1000 games (or Master System games that use the system's video modes like F-16 Fighter Falcon) or use its Japan only FM chip (the YM2413, which was also used on the MSX under the name MSX Music and was cloned by Konami as the VRC7 chip for the Famicom in Japan) unless the unit is modded. It also won't work with a 32X unless it is modded.
Sega CD: A CD-based add-on which would allow the Mega Drive to take advantage of a higher-capacity storage medium, enabling features such as Full Motion Video and Red Book CD sound. Unfortunately, the Mega Drive' own processing power wasn't quite enough to take advantage of these features to the fullest. Commonly believed to be a flop, the add-on actually sold well enough to be incorporated into some models of the console (the Wondermega and the CDX/Multi-Mega), though it never found the sort of popularity that the PC Engine's CD add-on did in Japan. Since the system remained bound by the Mega Drive's palette limitations (except for the few CD games that also supported the 32X add-on), live-action footage often turned into "the most horrifying, blurry, reduced-color-palette mess imaginable" (to quote Digital Pictures co-founder Ken Melville).
A 2nd 68000 chip running at 12.5 MHz, the main 68000 chip becomes the sound chips's CPU.
512 KB of main RAM and 256 KB of video RAM.
64 KB of sound RAM.
16 KB of CD drive cache.
8 KB of back up RAM, with memory cartridges going at 128 KB
Same as the Mega Drive but has a extra chip the can do scaling and rotation effects like the Super NES's Mode-7 chip (the Super NES has 2 PPUs, 1 for modes 0 to 6, and the other for mode 7) with the DPS1 chip and playing FMV video.
16 bit 8 channel PCM chip running at 32 KHz (44.1 KHz for CD-DA), also it's own CPU running at 12 MHz.
Sega 32X: Originally conceived as the Neptune, a cartridge-based 32-bit system to go with Sega's later CD-based system, the Sega Saturn, the add-on boasted two 32-bit processors and primitive 3D graphics capabilities, and was marketed as an opportunity for consumers to get a head start on the 32-bit generation. Unfortunately, both consumers and developers knew that the superior Saturn was just around the corner (even though Sega themselves believed the 32X and Saturn could co-exist, with casual gamers gravitating towards the cheaper 32X while the Saturn was reserved for the hardcore crowd), and titles for the add-on were few and far between. Some previous Sega CD games were also re-released on the 32X to take advantage of the system's improved processing.
2 Hitachi SH-2 chips, just like the Sega Saturn, but unlike the Saturn, the chip are a bit slower and are running at 23 MHz. each.
256 KB of main RAM and 256 KB (128 KB X 2) of video RAM.
256 KB of sound RAM
2 frame buffers with 2 layers (sprites and backgrounds) each (4 in total) and can be set up as just backgrounds or a large amount of sprites or ect.
32,768 Colors, no on screen limits.
50,000 sprites with their blocks going up to 512 X 512; Polygons like the Saturn are done with sprites, if all 4 layers are sprite layers, it can go up to 200,000 sprites.
Stuff like Scaling, Rotation and 3D Engines are done with software with said software running on the 2th SH-2 chip.
Screen resolution however is still the same as the Mega Drive.
2 10-bit PWM Channels.
Sega's apparent intention was for programmers to perform software mixing of music on one of the SH-2 chips, and use the PWM channels to play back the music, much like the Game Boy Advance several years later. While a few games attempted this (Kolibri in particular), the vast majority of games just used the Genesis's existing audio hardware for music, and the 32X's additional channels for sound effects.
Virtua Fighter 2: Actually a 2D version of the original 3D game with a lot of the content stripped out.
Virtua Racing: Notable for having the Sega Virtua Processor microchip, Sega's answer to the SNES's Super FX microchip, making it the second of two 100% real time 3-D video game available for the system. An upgraded version, Virtua Racing Deluxe, was made for the 32X, possibly to compensate for the fact that the original game won't play on a 32X equipped Sega Mega Drive.
Blatant Lies: The whole "Blast Processing" marketing was just hyping up the fact that the Mega Drive had a faster processor than the SNES.
Country Switch: It was found that many early region-free games actually does this. Depending on the game, changes may be as subtle as removing or adding a trade mark symbol to a complete overhaul (for example, Mystic Defender revealing itself to actually be a Peacock King game and reverting certain elements to its uncensored state).
Early-Installment Weirdness: The Mega Drive was more well known for its variety of big-name sports titles and arcade ports before Sonic gave the console a face in 1991.
Fan Nickname: A Sega Mega Drive with every possible add-on (A Power Base Converter, Sega CD, a 32X, a lock-on Sonic&Knuckles cartridge with Sonic 2 or 3 hooked in, possibly if you're feeling incredibly bold a Game Genie (as seen here) has been called the "Tower of Babel." Other names include the "Tower of Power" or the "Doom Tower".
Germans Love David Hasselhoff: The system was never a huge success in Japan compared to the Super Nintendo Entertainment System and the PC Engine (the Turbo Grafix-16 in Japan), but it was ridiculously popular in the rest of the world, especially North America and Europe. In fact, the Mega Drive outsold the SNES in countries like the United States and United Kingdom, thanks to being released two years before the SNES, promoting it as a more "edgy and cool" system, and the critical and commercial success of the Sonic the Hedgehog games. In fact, the only reason the SNES was able to outsell the Mega Drive in North America during the dying days of the 16-bit era was thanks to the release of Donkey Kong Country.
Polygon Ceiling: Towards the end of its life in the mid-nineties Sega attempted to create (at least the illusion of) 3D games on the system, such as with Sonic 3D Blast, Vectorman 2, certain levels in The Lost World and others. While the graphics were ambitious for a 16-bit system, the gameplay tended to suffer as a result. Virtua Racing managed to break through it thanks to using the Sega Virtua Processor chip to allow real time 3D graphics, but the added cost of this chip (which skyrocketed the game's cost to 100$) kept anymore games with the SVP from being made.
To add insult to injury, due to relying on certain hardware, Virtua Racing was incompatible with the Model 3 Genesis (unless you mod it) and pretty much all of the unofficial clone systems. So if you bought the game years later and happened to own a Model 3 system, you were SOL.
Product Facelift: The Mega Drive went through the most redesigns of any video game console in history—first, there's the model 1, which also has a link port (meant for the cancelled Sega Meganet) in the very, very earliest models, the more famous, streamlined model 2 Mega Drive, the Sega CDX which was a clever (but expensive) hybrid of the Mega Drive and Sega CD, the Model 3 Genesis from Majesco (Never released outside of North America), which was as big as the controller, and then there's the Sega Meganet/The Sega Nomad, both of which are literally portable Sega Mega Drive consoles! There is even a licensed version of the Mega Drive, first released in Europe, the AtGames Sega Mega Drive 20-in-1 Game Console, which contains 20 games built into the console and has Region Coding fully unlocked, is even smaller than the Model 3 Genesis, and has unofficially been dubbed the "Model 4 Genesis". This version made it to the United States shortly thereafter, and comes packed with 80 games.
There were two different types of Mega Drive controllers. The first is the classic three button Sega Mega Drive controller, and the second is a six button Mega Drive controller enhanced for fighting games such as Street Fighter (called a Sega Fighting Pad 6B in Japan). That's not even counting the Sega Menacer, a light gun peripheral which is Sega's answer to the Super Scope for the SNES, and the Sega Activator, which had clunky controls and ultimately failed to catch on.
Region Coding: Averted. The MegaDrive/Genesis was notable for not only being region-free early through the console's life, but even after region-locked games was introduced, it was found that the console can easily be modded because Sega made it so that changing the region of the console was as easy as moving some jumpers around on the motherboard, and thus it was trivial to mod the console just by soldering in some switches one can procure at most hobbyist outlets. You may still need to mod the case if you have a Japanese Mega Drive however (due to Japanese cartridges being of a slightly different shape), and a world-multi TV may be needed for out of region games.
Scapegoat Ad: Sega's famous anti-Nintendo commercials are fondly remembered by many a nostalgic Mega Drive fan. Unfortunately, when Sega began to be brought down by their failing add-ons, Nintendo took the opportunity to do their OWN Take That to Sega in the commercial for Donkey Kong Country, which advertised that such a technically ambitious game was NOT a Sega game and didn't need a CD or 32X adaptor to be played. Now the ads are Hilarious in Hindsight due to Sega falling out of the hardware business after the Sega Dreamcast.
Spin-Off: The Sega Pico contained pretty much the same main components as the Genesis/Megadrive save for replacing the OPN2 synthesizer with a uPD PCM DAC. A later Yamaha-made spinoff of the Pico reinstated the OPN2 synthesizer.
Video Game Long Runner: It was launched in 1988, and it wasn't formally discontinued until 1998. But, there are still versions of the console on sale today (and impressively, many of these clones are made under official license from Sega), and there were actually a few new unlicensed games released for it in the last decade, the most recent of which came out in 2012.
World of Ham: Pretty much anyone who appears in Sega's commercials.