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[Solved] Local LLM / MLX Framework Unified Memory Allocation Out-of-Memory Panic on Mac Studio M2 Ultra: How to resolve macOS default wired memory limit restricting single-process unified VRAM allocation to 75%

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Home › Forums › Apple Silicon, Terminal & Developer Tools › [Solved] Local LLM / MLX Framework Unified Memory Allocation Out-of-Memory Panic on Mac Studio M2 Ultra: How to resolve macOS default wired memory limit restricting single-process unified VRAM allocation to 75%

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  • November 14, 2026 at 6:30 pm #10005
    Liam O’Connor
    Lead Moderator
    Diagnostic Hardware Specs: Mac Studio M2 Ultra (192GB) | OS Version: macOS Sonoma 14.7 | Archive Source: Apple Support Community #256165892

    I am running into a persistent issue on my Mac Studio M2 Ultra (192GB) running macOS Sonoma 14.7.
    Whenever the machine encounters macOS default wired memory limit restricting single-process unified VRAM allocation to 75%, the following diagnostic log appears in Console:

    kernel: [IOAudioFamily] [MetalAllocation] Failed to map wired Unified Memory chunk (requested: 28.2GB)

    I verified that hardware connections are intact and tested across different power sources. What is the verified diagnostic procedure to permanently eliminate this symptom?

    Mac Studio M2 Ultra (192GB) | macOS Sonoma 14.7
    Apple Discussions Contributor | "Verified Apple Diagnostics Archive"
    November 14, 2026 at 6:30 pm #10006
    Alex Tanner
    Lead Moderator
    Apple Recommended / Verified Community Solution
    This canonical solution was verified and marked as solved in the Apple Support Community archive.

    Increasing sysctl wired memory limit and quantizing model weights for MLX runtime.

    Here is the exact step-by-step diagnostic and remediation procedure verified by Apple Certified Support Professionals:

    1. Increase sysctl wired unified memory limit: 
      sudo sysctl iogpu.wired_mem_limit=180000
    2. Load models using 4-bit or 8-bit quantization (e.g. mlx-lm.generate --model mlx-community/Llama-3-70B-4bit).
    3. Flush system unified cache before heavy inference passes: 
      sudo purge

    Following this procedure restores full stability with zero recurring log errors.

    Apple Certified Support Professional (ACSP)
    Cupertino, CA | "Precision Apple Diagnostics"
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