In this paper, we present a system architecture currently under development that will allow very large (>10^6 neurons, >10^9 synapses) reconfigurable networks to be built, in the form of interlinked dies on a single wafer. Reconfigurable routing and complex adaptation/plasticity across several timescales in neurons and synapses allow for the implementation of large-scale biologically realistic neuronal networks and behaviors. Compared to biology the network dynamics will be about 104 to 105 times faster, so that developmental plasticity can be studied in detail.