Apple M5 Max Falls 11x Short of Real-Time Diffusion Video at 1.4 FPS vs 16 FPS Target
A developer benchmarking autoregressive diffusion video generation on an Apple M5 Max found the system produced just 1.418 native frames per second, far below the pre-defined real-time threshold of 16 FPS — an 11.28× gap. The tests used a Wan2.1-T2V-1.3B-based causal video model and were conducted under strict pre-registered protocols, with prompts, seeds, and thresholds locked before any results were seen. One meaningful systems improvement was identified: increasing MLX's bounded free-buffer cache from 1 GiB to 4 GiB cut total generation wall time by about 17%, from 69 to 57 seconds. Profiling revealed that causal VAE decoding alone accounted for 72–79% of total wall time, making the decoder — not the transformer — the primary bottleneck. The researcher published the findings and a reproducible verification repository despite missing the real-time target, arguing the measured bottlenecks and rejected hypotheses hold independent value.
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