Abstract: There is provided a neural network processor system including: a plurality of neural processing units, including a first neural processing unit and a second neural processing unit, whereby each neural processing unit comprises an array of neural processing core blocks, each neural processing core block comprising a neural processing core; and at least one central processing unit communicatively coupled to the plurality of neural processing units and configured to coordinate the plurality of neural processing units for performing neural network computations. In particular, the first and second neural processing units have a different structural configuration to each other. There is also provided a corresponding method of operating and a corresponding method of forming the neural network processor system.