A hardware erratum in the Apple M3 Neural Engine limits DRAM weight streaming to 17–19 GB/s, far below the nominal 45–60 GB/s. The issue stems from a problematic path in the kernel DMA engine's speculative prefetch ring. Bypassing this path restores performance, doubling Llama 3.2 1B token throughput from 10.0 to 24.3 tokens/s.
- M3 Neural Engine DRAM throughput is capped at 17-19 GB/s due to a hardware erratum.
- The bottleneck lies in the kernel DMA engine's speculative prefetch ring logic.
- Avoiding the errant path doubles Llama 3.2 1B inference speed to 24.3 tokens/s.
- Workarounds require kernel-level adjustments to DMA prefetch behavior.