Abstract: A smart network interface controller (NIC) implemented using a stacked die configuration is provided. The NIC may include user-customizable networking circuits formed in a top programmable die and primitive network function blocks formed in a bottom application-specific integrated circuit (ASIC) die. The top programmable die may provide a flexible packet processing pipeline to facilitate efficient control and data communication between the user-customizable networking circuits and the primitive network function blocks. The bottom ASIC die may also include an array of memory blocks operable as lookup tables and intermediate buffers for other network processing circuitry in the NIC. A NIC configured in this way provides both performance, power, and area benefits and superior customer configurability.