# Apple Mac Studio M5 Ultra 512GB for local LLMs

> The largest memory pool in a single desktop, with about 1.2TB/s of bandwidth to feed it.

The M5 Ultra 512GB has 512GB of unified memory (about 384GB usable by the GPU by default) and 1,228 GB/s of memory bandwidth, which decides how big a model fits and how fast it generates text. It comfortably runs models up to about 320B parameters: the largest in our catalog is GLM-5.3-Flash at Q6_K (273GB with 8K context, ~25 tokens/sec).

## Key specs

- Memory: 512GB LPDDR5X (unified; ~384GB usable by the GPU by default)
- Memory bandwidth: 1,228 GB/s
- Architecture: Apple M5 Ultra (2026)
- Power: 480W
- Typical price: n/a (checked 2026-10)
- Software: Metal, MLX

## Best models for this GPU

- **Best overall (also coding, reasoning, vision):** GLM-5.3-Flash at Q6_K, ~272.6GB with 8K context, ~25 tokens/sec
- **Runner-up:** DeepSeek V4 Flash at FP4, ~167.5GB with 8K context, ~45 tokens/sec
- **Fastest good model:** gpt-oss-20b at MXFP4, ~15.0GB with 8K context, ~105 tokens/sec
- **Largest model that fits:** GLM-5.3 at Q3_K_M, ~374.9GB with 8K context, ~19 tokens/sec

## Compatibility (best quantization that fits, 8K context)

| Model | Params | Quant | Memory | Speed | Verdict |
| --- | --- | --- | --- | --- | --- |
| Gemma 4 E4B | 8B | Q8_0 | 10.5GB | ~64 tok/s | Runs well |
| Qwen3.5 9B | 9B | Q8_0 | 12.0GB | ~57 tok/s | Runs well |
| Phi-4 | 14.7B | Q8_0 | 18.3GB | ~41 tok/s | Runs well |
| gpt-oss-20b | 20.9B (3.6B active) | MXFP4 | 15.0GB | ~105 tok/s | Runs well |
| Gemma 4 26B A4B | 26B (3.8B active) | Q8_0 | 29.5GB | ~73 tok/s | Runs well |
| Qwen3.8 27B | 27B | Q8_0 | 31.6GB | ~22 tok/s | Runs well |
| Gemma 4 31B | 31B | Q8_0 | 35.9GB | ~20 tok/s | Runs well |
| Qwen3.6 35B-A3B | 35B (3B active) | Q8_0 | 41.0GB | ~83 tok/s | Runs well |
| GLM-4.5-Air | 106B (12B active) | Q8_0 | 118.1GB | ~28 tok/s | Runs well |
| Llama 4 Scout | 109B (17B active) | Q8_0 | 120.2GB | ~21 tok/s | Runs well |
| gpt-oss-120b | 117B (5.1B active) | MXFP4 | 68.3GB | ~93 tok/s | Runs well |
| Qwen3.5 122B-A10B | 122B (10B active) | Q8_0 | 134.3GB | ~33 tok/s | Runs well |
| DeepSeek V4 Flash | 284B (13B active) | FP4 | 167.5GB | ~45 tok/s | Runs well |
| GLM-5.3-Flash | 320B (18B active) | Q6_K | 272.6GB | ~25 tok/s | Runs well |
| GLM-5.3 | 744B (40B active) | Q3_K_M | 374.9GB | ~19 tok/s | Fits, tight |

## Pros
- 512GB of unified memory in one desktop
- About 1.2TB/s of memory bandwidth
- Quiet, efficient and simple to set up with MLX or llama.cpp
- Neural Accelerators improve prompt processing over earlier Macs

## Cons
- Price not announced as of October 2026
- No CUDA, so some tools and fine-tuning workflows do not run
- Memory cannot be upgraded after purchase

Full page: https://llamabuilds.ai/gpus/mac-studio-m5-ultra-512gb · Best models: https://llamabuilds.ai/gpus/mac-studio-m5-ultra-512gb/best-models

Sources: [Apple Mac Studio (M5 Max or M5 Ultra) tech specs](https://support.apple.com/en-us/128107), [MacRumors: Mac Studio with M5 Ultra and 512GB launching in October](https://www.macrumors.com/2026/08/25/mac-studio-m5-ultra-512gb-ram-october/), [Apple Mac Studio power consumption and thermal output](https://support.apple.com/en-us/102027), [ModelPiper: raising the Metal memory ceiling with iogpu.wired_limit_mb](https://modelpiper.com/blog/iogpu-wired-limit-mb-mac)

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Source: https://llamabuilds.ai/gpus/mac-studio-m5-ultra-512gb · Updated October 14, 2026 · Llama Builds. Speeds marked ~ are estimates from our bandwidth model (https://llamabuilds.ai/methodology); measured results are labeled as such.