The Sega Mega Drive (Sega Genesis in North America) was developed and produced by Sega.
Lots of :words: about the console.
Physical tech specs.
Programming / Hacking details.
The language and video mode of the Mega Drive is controlled by two jumpers on the circuit board, connecting them high or low will change language between Japanese and English and 50/60Hz. Note that RGB output is needed for color if the frequency is changed from factory settings unless you replace a crystal as well.