Why Mobile GPU Inference Hits a 2.5× Speed Ceiling: The VRAM Math Explained

Developers optimizing LLM inference on mobile devices encounter a mathematical ceiling: GPU acceleration alone can't overcome the bottleneck of memory-intensive layers like vocabulary projection. This analysis quantifies that limit, showing how hybrid CPU-GPU offloading achieves 2.5× speedup on 4GB hardware and explaining why exceeding that threshold requires architectural changes, not just more GPU memory.