Figure 9.

The configuration space of STDP on discrete weights spanned by the weight resolution r and the number n of SSPs that is inversely proportional to the weight update frequency v_w. The darkest gray area depicts the configurations with dead discrete weights (Figure 3). The lower limits of configurations for proper equilibrium weight distributions (Figure 4) and single synapse dynamics (Figure 6) are shown with brighter shades. The dashed rectangle marks configurations realizable by the FACETS wafer-scale hardware system (assuming an acceleration factor of 10³, all synapses enabled for STDP and SSPs applied with 10 Hz). The working points for a 4-bit (n = 36) and 8-bit (n = 12) weight resolution are highlighted as a triangle and circle, respectively.