Bugs:Alex Kidd in The Enchanted Castle
This page details bugs of Alex Kidd in The Enchanted Castle.
|Scopaco Cycle (YM2612)||Scopaco Cycle (YM3438)|
While it's debatable that this can be called a software bug in the traditional sense, Alex Kidd utilizes a hardware bug for volume levelling certain sounds in the background music. Alex Kidd's background music was written in a period where all Mega Drives (and by extension, the Genesis) used the YM2612 chip.
The YM2612 internally has a volume bug that incorrectly quantizes low volume audio, causing a distortion and a flawed volume curve. This has been dubbed low volume distortion, or LVD for short for its distinctive "crunchy/buzzy" qualities akin to a guitar run through a distortion amplifier. All games pre-1994 were written around this improper volume curve, with Alex Kidd using LVD to make quieter sounds louder than they actually are, and to sustain the volume of louder sounds as they fade in volume. In Scopaco Cycle, it's used to emphasize a otherwise quiet melody and extend the length of the snares.
In 1994, SEGA released a revision to the Mega Drive/Genesis dubbed the Model 2. Internally, the Model 2 uses the YM3438 chip that fixes the LVD bug and gives a higher quality sound. Later games would be written with the Model 2 in mind, but for earlier games the volume curve was broken. Some games were mostly unaffected, but others like Alex Kidd, Batman, and After Burner II sound different from the two models with certain songs from those games having different volume mixing.
Absence of TMSS
The Japanese version of Alex Kidd does not run on later Model 1 and Model 2 consoles, as it fails one of the checks that the TradeMark Security System requires for games to boot. This can be bypassed by using a Game Genie with the game cartridge, allowing it to run on all models. International copies of the game later added the check necessary for the TMSS to work.
In Japan, Alex Kidd was released before the implementation of the TradeMark Security System. It's believed by sites such as SEGA Retro that instead of deterring pirates, it was originally intended to deter import copies before somewhere along the way, SEGA decided that this wasn't going to work; future Japanese consoles and games would later implement TMSS in one way or another.