Techniques in electronic systems, such as in systems including a processing chip and one or more external memory chips, provide improvements in one or more of system security (such as intrusion and/or virus/malware prevention), performance, cost, and efficiency. For example, the processing chip includes at least one CPU and circuitry enabling the at least one CPU to securely boot from an external, non-volatile memory chip containing encrypted, executable code. The circuitry comprises immutable hardware to copy the executable code from the non-volatile memory to another external memory from which the at least one CPU is able to access it. The encryption uses a key created at a manufacturing time of and unique to the processing chip that is never CPU-accessible, forming a secure hardware association between the processing chip and the non-volatile memory chip.