RetroVision – Sonic’s Lock-On Technology

Sonic 3 & Knuckles is one of my favourite game’s of all time, an essential 16-bit title and a platformer you really shouldn’t be without.  However, whilst both Sonic 3 and Sonic & Knuckles were released separately, they were always intended to be the one game.  They are two parts of one story, and quite honestly should only be played together.

The reason for their separation into two games was not something done by design, but rather an unfortunate consequence of the grand design scope that Sonic Team and the game’s primary directors Yuji Naka and Hirokazu Yasuhara had.  The game was initially always planned to be released on one cartridge as simply Sonic 3, however this would have meant utilising expensive 32mb NVRAM cartridges, and this combined with time constraints forced SEGA into making the decision to split the game into two halves.  A decision that was made as an alternative to reducing the scope of the game or to postponing its release.  With postponing the game seen as a potentially disastrous move given that the SEGA Saturn would release in Japan only a month after Sonic & Knuckles.

Hidden Palace
Sonic Vs Knuckles in the Hidden Palace Zone

The decision to split the game in half not only bought Sonic Team time to polish and perfect the title, it also allowed them to add extra features that were not originally planned.  The most important of these being the ability to save the game, a feature not seen as a standard in the early 90s and one that would become vital to making the two games feel whole.  However, whilst the decision to split the game’s development and release had many benefits, it left one critical problem – how to keep the game as one whole experience rather than simply a game and its sequel.  Sonic Team and SEGA were determined to keep the experience as one game and came up with a very unique solution to this problem, lock-on cartridge technology.

Most will remember the unique ability to “lock” other Mega Drive / Genesis games onto the top of Sonic & Knuckles.  In fact, the game’s lock-on technology has in many ways become one of the most memorable hardware creations of the 16-bit era.  This technology works by utilising a specific set of circuitry to combine multiple ROM chips together, creating one single address space.  This in turn makes the console believe that only one cartridge is inserted, that cartridge actually being the combination of the two.  This shouldn’t be confused with the technology behind Game Genie and other cheat cartridges, which run both the device’s internal programming and the game cartridge itself separately.

Sonic & Knuckles Advert
Advert for Sonic & Knuckles

This technology allowed SEGA and Sonic Team to achieve their original design concept for Sonic 3, with the game’s complete form commonly referred to by both the industry and SEGA themselves as Sonic 3 & Knuckles.  SEGA at the time marketed this technology as “the only backwards-compatible game cartridge”, but in actual fact it could easily be argued that Sonic & Knuckles was in many ways one of the earliest forms of additional content or DLC.  This is backed up by the notion that many of the assets required for Sonic & Knuckles can be found within Sonic 3 due to the notion of the two games eventually needing to become one.  Seen clearly within Sonic 3’s level select screen which features inaccessible levels and music from Sonic & Knuckles despite the games launch’s being 10 months apart.

By combining the two games together, players are able to experience the complete story all in one go.  As such gamers are able to immediately chase after Eggman as he crash lands onto the Floating Island after his defeat at the Launch Base Zone, all whilst using Sonic 3’s save function which isn’t present in Sonic & Knuckles.  Moreover, not only are players treated to Knuckles as a playable character within Sonic 3, but they can also take Tails over into Sonic & Knuckles, both of which are not possible if the games are played in isolation.

Knuckles 2
Knuckles in Sonic 2

In fact, there are a wealth of additions to the game that make you question why all these years later anyone would think of playing the two games separately.  What’s more, combining the two games together is the only way to gain the hidden Super Emeralds which transform Sonic, Tails & Knuckles into their “Hyper” counterparts.  These are accessed through special stages hidden within Sonic & Knuckles which can only be found after first collecting all of the Chaos Emeralds in Sonic 3, and then continuing the same game through into Sonic & Knuckles.

The lock-on technology that SEGA created didn’t only grant enhancements to Sonic 3 though.  It also breathed new life into Sonic 2, allowing gamers to play through the the game’s stages as Knuckles, whilst also changing aspects such as item locations.  This actually adds much more to the game than you might first think, as by utilising Knuckles’ ability to glide and climb walls, not only can new approaches to pre-explored levels be taken, but new areas can even be discovered.  Furthermore, lock-on also gave players the ability to play a more extensive version of Sonic & Knuckles’ special stages, known as ‘Get The Blue Spheres’.  This is accessed by combining the game with either the original Sonic the Hedgehog, or other select Mega Drive / Genesis titles in order to play the mini game.  Though it first required players to press A, B & C simultaneously to pass the infamous “No Way!” screen.

Sonic No Way
No Way Screen

Ultimately SEGA’s lock on technology has become one of the most memorable pieces of technology from the 16-bit era, and justifiably so.  Thanks to lock-on technology not only were players able to experience the complete Sonic 3 & Knuckles experience, but they were also provided with both a brand new take on Sonic the Hedgehog 2, and even a mini game on top of that.  In many ways it once again represents how SEGA was ahead of the curve, as delivering extra content post-release has now become commonplace in the market through DLC, and in many ways this is exactly what Sonic & Knuckles offered.

Sophia Aubrey Drake

A lifelong gamer with a fanatical love of all things Nintendo and Japan. So much so that she's written a thesis on one and lived in the other. Currently on a quest to catch every last Pokémon. Follow me on twitter via @DivaXChill or @RingsandCoins.

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