An embodiment of this invention uses a massive parallel interconnect fabric (MPIF) at the flipped interface of a core die substrate (having the core logic blocks) and a context die (used for in circuit programming/context/customization of the core die substrate), to produce ASIC-like density and FPGA-like flexibility/programmability, while reducing the time and cost for development and going from prototyping to production, reducing cost per die, reducing or eliminating NRE, and increasing performance. Other embodiments of this invention enable debugging complex SoC through large contact points provided through the MPIF, provide for multi-platform functionality, and enable incorporating FGPA core in ASIC platform through the MPIF. Various examples are also given for different implementations.