Can Mac Studio M5 Ultra 256 GB run Reflection Beam (501B-A23B)?
256 GB unified · 1228 GB/s memory bandwidth · Reflection Beam (501B-A23B) has 501B parameters (23B active per token).
Short answer
No. It doesn't fit in memory.
Needs ≈265 GB but only ≈246 GB is available after the OS, other apps and Open WebUI.
Why it doesn’t fit
Even its smallest practical version (MXFP4) needs about 265 GB for the model, its context memory and the runtime. After macOS (≈6.0 GB), a browser with a few tabs (≈3.0 GB) and Open WebUI (≈1.0 GB), Mac Studio M5 Ultra 256 GB has about 246 GB left, so it’s 19 GB short.
Ways to make it work
Close everything else
Not enough on its own: with every other app closed it’s still about 16 GB short.
Pick a smaller model from the same family
No smaller Beam model in our catalog runs well here. See the other models below.
Get more memory
The same chip with 512 GB handles it: Excellent.
Check your exact setup
These pages assume typical settings. A shorter context or a lighter chat app can change the answer.
Check Mac Studio M5 Ultra 256 GB
The same applies to every workload we rate (chat, coding questions, coding in a repository, agentic coding and long documents): they all need at least as much memory as chat.
Other models for Mac Studio M5 Ultra 256 GB
The best-rated models for chat on this machine.
- gpt-oss-120b120–210 tok/sExcellent
- Qwen3.6 35B-A3B140–240 tok/sExcellent
- Qwen3-Next 80B-A3B Instruct140–230 tok/sExcellent
- Gemma 4 26B-A4B110–190 tok/sExcellent
- Qwen3.5 35B-A3B140–240 tok/sExcellent
- LFM2.5 24B-A2B280–460 tok/sExcellent
Cheapest machines for Reflection Beam (501B-A23B)
Hardware rated comfortable or better for chat, lowest price first.
Different tool, context size or workload?
These pages use typical settings. The full check models your exact setup.