A chip package comprises an interposer; an FPGA IC chip over the interposer, wherein the FPGA IC chip comprises a programmable logic block configured to perform a logic operation on its inputs, wherein the programmable logic block comprises a look-up table configured to be provided with multiple resulting values of the logic operation on multiple combinations of the inputs of the programmable logic block respectively, wherein the programmable logic block is configured to select, in accordance with one of the combinations of its inputs, one from the resulting values into its output, and multiple non-volatile memory cells configured to save the resulting values respectively; multiple first metal bumps between the interposer and the FPGA IC chip; and an underfill between the interposer and the FPGA IC chip, wherein the underfill encloses the first metal bumps.