SDAA185 February 2026
The comparison between CPU and NPU execution reveals important insights that should guide implementation decisions:
NPU Advantages for Complex Models: For larger models, the NPU delivers significant performance improvements. The 128-neuron model runs 29.7% faster on the NPU than on the CPU (0.7116ms vs 1.012ms latency), while the 64-neuron model shows a 20.7% latency reduction. This advantage stems from the NPU's specialized architecture for parallel neural network computations.
CPU Advantage for Simple Models: Interestingly, for very small models like the 16-neuron configuration, the CPU actually outperforms the NPU. The CPU achieves 44,643 samples/sec compared to the NPU's 39,557 samples/sec—a 12.9% performance advantage. This counterintuitive result stems from the overhead associated with transferring data to and from the NPU. For the 16-neuron model, the computational workload is so minimal that the CPU can process it directly within its native execution environment, avoiding multiple data transfer steps. With such a small model, the CPU completes the entire inference in a single execution context without the memory transfer penalties that the NPU incurs. Every NPU inference requires setting up DMA transfers, configuring the accelerator, waiting for completion, and retrieving results—operations that collectively consume more time than the actual neural network computation for this lightweight model. Essentially, when the model is this small, the "cost" of using the specialized hardware exceeds its computational benefit.