AbstractPhotonic neuromorphic computing may offer promising applications for a broad range of photonic sensors, including optical fiber sensors, to enhance their functionality while avoiding loss of information, energy consumption, and latency due to optical‐electrical conversion. However, time‐dependent sensor signals usually exhibit much slower timescales than photonic processors, which also generally lack energy‐efficient long‐term memory. To address this, a first implementation of physical reservoir computing with non‐fading memory for multi‐timescale signal processing is experimentally demonstrated. This is based on a fully passive network of 64 coupled silicon microring resonators. This compact photonic reservoir is capable of hosting energy‐efficient nonlinear dynamics and multistability. It can process and retain input signal information for an extended duration, at least tens of microseconds. This reservoir computing system can learn to infer the timing of a single input pulse and the spike rate of an input spike train, even after a relatively long period following the end of the input excitation. This operation is demonstrated at two different timescales, with approximately a factor of 5 difference. This work presents a novel approach to extending the memory of photonic reservoir computing and its timescale of application.