Memory at each precision
| Version | Weights | With context | Smallest Mac |
|---|---|---|---|
| 8-bit | 131 GB | 141 GB | 192 GB |
| 6-bit | 99.9 GB | 108 GB | 192 GB |
| 4-bit | 69.2 GB | 74.7 GB | 128 GB |
| 3-bit lower quality | 53.8 GB | 58.1 GB | 96 GB |
| 2-bit lower quality | 38.4 GB | 41.5 GB | 64 GB |
On every Apple chip
The smallest memory size of each chip that runs Devstral 2 (123B), the best version that fits it, and the writing speed you can expect.
| Chip | Needs | Version | Tokens/s |
|---|---|---|---|
| M6 | no size fits | Too big | – |
| M5 Ultra | 256 GB | 8-bit Slow | 4–7 |
| M5 Max | 128 GB | 4-bit Slow | 4–7 |
| M5 Pro | 64 GB | 2-bit Slow | 4–6 |
| M5 | no size fits | Too big | – |
| M4 Max | 128 GB | 4-bit Slow | 4–6 |
| M4 Pro | 64 GB | 2-bit Slow | 3–6 |
| M4 | no size fits | Too big | – |
| M3 Ultra | 256 GB | 8-bit Slow | 3–5 |
| M3 Max | 128 GB | 4-bit Slow | 3–5 |
| M3 Pro | no size fits | Too big | – |
| M3 | no size fits | Too big | – |
| M2 Ultra | 128 GB | 4-bit Slow | 5–9 |
| M2 Max | 64 GB | 2-bit Slow | 5–8 |
| M2 Pro | no size fits | Too big | – |
| M2 | no size fits | Too big | – |
| M1 Ultra | 128 GB | 4-bit Slow | 5–9 |
| M1 Max | 64 GB | 2-bit Slow | 5–8 |
| M1 Pro | no size fits | Too big | – |
| M1 | no size fits | Too big | – |
How to run it
- The easy way: download MLX Harness, free and open source. Search for Devstral 2 (123B), download the version that fits your Mac, and chat. It also serves the model to your other apps over an OpenAI-compatible API.Download MLX HarnessFree · Apple Silicon · macOS 14.5 or later
- In Terminal with Apple’s MLX:
pip install mlx-lmmlx_lm.chat --model mlx-community/Devstral-2-123B-Instruct-2512-4bitBuild: mlx-community/Devstral-2-123B-Instruct-2512-4bit on Hugging Face. Other precisions sit next to it.
Step by step: download and run LLMs on a Mac · how to use MLX Harness · MLX vs Ollama vs llama.cpp
About Devstral 2 (123B)
| Made by | Mistral AI |
|---|---|
| Parameters | 123B (dense) |
| Context | 256K tokens |
| Licence | Modified MIT |
| Released | 2025-11 |
| Input | Text |
| Weights | mistralai/Devstral-2-123B-Instruct-2512 |
Questions
- How much memory does Devstral 2 (123B) need?
- About 69.2 GB of weights at 4-bit, plus room for the context: 74.7 GB in all. On a Mac that means 128 GB of unified memory or more, since macOS lets the GPU use about 75% of it by default.
- How fast is Devstral 2 (123B) on a Mac?
- Writing speed depends on memory bandwidth. The fastest Mac for it here is an M2 Ultra with 128 GB at about 5–9 tokens a second (4-bit). The smallest Mac that runs it, with 128 GB, manages about 5–9 on an M2 Ultra.
- Does quantization hurt Devstral 2 (123B)?
- At 4 bits most models stay close to the original quality; below 4 bits quality drops faster. Pick the highest precision that fits your Mac with room to spare.
Similar models
For your model card or README
Shows the smallest Mac that runs Devstral 2 (123B) well and links here.
[](https://mlx.app/run/devstral-2-123b)How it’s worked out
Memory: the model’s parameters at 8, 6, 4, 3 or 2 bits per weight plus MLX’s group scales (half a bit per weight), or its native format, with room for the context on top. By default macOS lets the GPU use about 75% of unified memory. Speed: memory bandwidth divided by the bytes read per token is the ceiling for one conversation; in llama.cpp’s public Apple Silicon benchmarks real runs reach about 45% to 80% of it, which is the range shown. These are estimates, not measurements: measure your own Mac on MLX Bench. Model figures from each official model card, chip figures from Apple’s Tech Specs. Checked 2026-10-19. Same data as mlx.app/compare.