System configurations and techniques for implementation of a neural network in neuromorphic hardware with use of external memory resources are described herein. In an example, a system for processing spiking neural network operations includes: a plurality of neural processor clusters to maintain neurons of the neural network, with the clusters including circuitry to determine respective states of the neurons and internal memory to store the respective states of the neurons; and a plurality of axon processors to process synapse data of synapses in the neural network, with the processors including circuitry to retrieve synapse data of respective synapses from external memory, evaluate the synapse data based on a received spike message, and propagate another spike message to another neuron based on the synapse data. Further details for use and access of the external memory and processing configurations for such neural network operations are also disclosed.