Abstract: A computer system having multiple processors wired to a common MCM substrate in which insertable processor chips themselves carry fencing appropriate to their function on the multi-chip module in which they are inserted for optimizing needed functions with fencing of interfaces to permit cryptographic functions to be added by inserting a cryptographic by providing each processor of the multichip module with its own cryptographic coprocessor as needed enabling alternative configurations of the computer system using a common substrate but differing processing units and cryptographic coprocessors.