The STI Design Center opened in March 2001. The Cell was designed over a period of four years, using enhanced versions of the design tools for the POWER4 processor. Over 400 engineers from the three companies worked together in Austin, with critical support from eleven of IBM's design centers. During this period, IBM filed many patents pertaining to the Cell architecture, manufacturing process, and software environment. An early patent version of the Broadband Engine was shown to be a chip package comprising four "Processing Elements", which was the patent's description for what is now known as the "Power Processing Element" (PPE). Each Processing Element would contain 8 ""Synergistic Processing Elements"" (SPEs) on the chip. This chip package was supposed to run at a clock speed of 4 GHz and with 32 SPEs providing 32 gigaFLOPS each (FP8 quarter precision), the Broadband Engine was meant to have 1 teraFLOPS of raw computing power in theory.