These years may seem early for a story on the History Of The PS3, but these dates will be understood as you read further into the PS3 history.(Thanks to winocm, for making me go back this far :p).
During the year 2000, Sony Computer Entertainment, Toshiba, and IBM(STI),formed an alliance, an alliance that would see the creation of the Cell Processor, Cell is short for Cell Broadband Engine Architecture.
The STI design center opens and begins production of the Cell processor, this would be a four year endeavor, which would lead you to 2005.
Part of the above is sourced from Wikipedia.