Catalyst N2: Full Loihi 2 Feature Parity in an Open Neuromorphic Processor with Programmable Neuron Microcode and Cloud FPGA Validation

I present Catalyst N2, the second generation of the Catalyst neuromorphic processor architecture, achieving full feature parity with Intel's Loihi 2. Building on the Catalyst N1 foundation of 128 cores with 131K neurons and Loihi 1 equivalence, N2 introduces a programmable neuron microcode engine that replaces the fixed CUBA integrate-and-fire model with user-defined neuron dynamics — enabling Izhikevich, adaptive LIF, sigma-delta, and resonate-and-fire models to execute natively on the same silicon. Four graded spike payload formats (binary through 24-bit), variable-precision weight packing (1–16 bit), convolutional synapse encoding, per-synapse-group plasticity control, and a hierarchical dendritic compartment tree with per-dendrite thresholds round out the architectural extensions. The accompanying SDK has grown from 14 modules and 168 tests (N1) to 88 modules and 3,091 tests across three backends: a cycle-accurate CPU simulator with hardware-accurate fixed-point defaults, a GPU simulator with stochastic rounding in the learning path for silicon-faithful weight evolution, and an FPGA hardware backend. Hardware-accurate defaults, 24-bit fixed-point arithmetic, strict SRAM budget enforcement, and 7-bit learning trace registers are enabled by default, ensuring that every simulation faithfully represents what the hardware would produce. I validate a 16-core instance on an AWS F2 Xilinx VU47P at 62.5 MHz, achieving 28/28 (100%) pass rate across seven test categories spanning single-neuron dynamics, synaptic connectivity, network topologies, multi-core routing, scale, and operational correctness. Feature coverage analysis identifies 155 Loihi 2 features, of which 152 are fully implemented and 3 are hardware-only (requiring physical multi-chip links). The Spiking Heidelberg Digits benchmark from N1 is preserved at 85.9% accuracy. Catalyst N2 is, to my knowledge, the first independently developed neuromorphic architecture to achieve comprehensive Loihi 2 parity and the first to be validated on cloud FPGA infrastructure.