In the 70s, Maxon used the JRC4558 chipset and successfully created a much sought after overdrive pedal. Soon after, Ibanez, Boss and other pedal makers started to make use of this chipset and made JRC4558 so famous. With technology, we can use even better quality JRC4558 chipsets to get a better sound!
OD-8 biggest breakthrough in technology is that the OD-8 allows the user to change the chipset to create different tone he or she desires without soldering and the expertise of professionals, just like a changing a processor of a computer.