Mac Studio M3 Ultra 256GB

Apple’s 2025 workstation built on the M3 Ultra (March 2025 announcement), the first Mac with 512GB of unified memory. Three configurations: 96GB at $3,999, 256GB at $5,499, 512GB at $7,499. All share 819 GB/s of memory bandwidth and a 100W-class chip.

What it does well:

• 512GB in one box: at launch it was the only consumer machine that could hold DeepSeek R1 or Kimi-class checkpoints whole, no offloading.
• Efficiency: a full inference node at 100W of chip power - roughly a tenth of a comparable multi-GPU server’s draw.

Where it falls short: MLX and GGUF runtimes, no CUDA; 819 GB/s is well below the M4/M5 Ultra tiers, so tok/s on large models trails them. Apple has superseded it twice since, and the M5 Ultra beats it on every spec.

Run it locally: LM Studio, Ollama, or mlx-lm. Check the modeldex results for fit and estimated tok/s per checkpoint on your memory tier.