# Apple Mac Studio M5 Ultra 256GB for local LLMs

> Most of what the M5 Ultra offers, with 256GB, shipping now at $9,499.

The M5 Ultra 256GB has 256GB of unified memory (about 192GB 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 Q3_K_M (161GB with 8K context, ~39 tokens/sec). Our top all-round pick for it is DeepSeek V4 Flash (FP4, ~45 tokens/sec).

## Key specs

- Memory: 256GB LPDDR5X (unified; ~192GB usable by the GPU by default)
- Memory bandwidth: 1,228 GB/s
- Architecture: Apple M5 Ultra (2026)
- Power: 480W
- Typical price: ~$9,499 (checked 2026-10)
- Software: Metal, MLX

## Best models for this GPU

- **Best overall (also coding, reasoning):** DeepSeek V4 Flash at FP4, ~167.5GB with 8K context, ~45 tokens/sec
- **Runner-up (also vision):** Qwen3.8 27B at Q8_0, ~31.6GB with 8K context, ~22 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-Flash at Q3_K_M, ~161.4GB with 8K context, ~39 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) | Q3_K_M | 161.4GB | ~39 tok/s | Runs well |
| GLM-5.3 | 744B (40B active) | - | - | - | Won't fit |

## Pros
- 256GB of fast unified memory, available now
- About 1.2TB/s of bandwidth
- Quiet and power efficient

## Cons
- Cannot fit 600B-plus models at 4 bit
- No CUDA support
- Memory is fixed at purchase

Full page: https://llamabuilds.ai/gpus/mac-studio-m5-ultra-256gb · Best models: https://llamabuilds.ai/gpus/mac-studio-m5-ultra-256gb/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/), [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-256gb · Updated October 14, 2026 · Llama Builds. Speeds marked ~ are estimates from our bandwidth model (https://llamabuilds.ai/methodology); measured results are labeled as such.