A pre-registered study measures the severe memory bandwidth wall for serving 235B-parameter Mixture-of-Experts models on consumer hardware, where decode speeds drop to 0.44 tok/s due to SSD-bound expert streaming. Researchers developed llama-moe-trace to analyze routing on Qwen3-30B, revealing that while adjacent-token expert reuse offers a 2.0x chance and 95% of traffic hits only 52.5% of experts, this locality is insufficient to overcome paging thrash at scale. The work presents a negative result for training routers specifically for cache locality, as batching schemes collapse under disk I/O pressure.
- 235B MoE decode on 8GB GPU is I/O bound, not compute bound, hitting 0.44 tok/s due to SSD latency.
- llama-moe-trace tool enables zero-surgery telemetry to quantify expert routing patterns and cache misses.
- 95% of Qwen3-30B traffic accesses only 52.5% of experts, showing inherent but insufficient locality.
- Batching schemes designed to amortize disk sweeps collapse at batch 32 due to paging thrash.
- Training routers for cache locality against the edge bandwidth wall proved ineffective in this study.