Custom CUDA shim runs Stable Diffusion on Mac faster than RTX 5090 on Windows, up to 61% quicker

LioDavinchy · reddit · 2026-09-21

A Reddit user demoed macuda, a CUDA driver/shim layer that lets Macs run CUDA software natively—and Stable Diffusion runs faster than the same RTX 5090 under Windows.

Benchmarks used the same 5090 in the same Thunderbolt enclosure on both machines, comparing warm image-generation times: SDXL Turbo 2.56s vs 4.11s (+61%), SD 1.5 +22%, Z-Image Turbo +19%, Qwen-Image +16%, Qwen-Image 2.1 +12%. The author says all CUDA software now runs at parity, with diffusion workloads 12–61% faster depending on the model—an unintuitive result for the Mac local image-gen ecosystem.

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