Is unified memory on Mac Studio M2 Ultra 64GB as fast as VRAM for stablelm 2 zephyr 1 6b?

Not always. Mac Studio M2 Ultra 64GB can often fit larger models thanks to unified memory, but a discrete GPU with dedicated high-bandwidth VRAM may still decode faster once the model fits. For this combination, the important distinction is capacity versus sustained throughput.

Can stablelm 2 zephyr 1 6b run on Mac Studio M2 Ultra 64GB?

YES — Runs Great

C47Usable

Estimated from fit model

stablelm 2 zephyr 1 6b needs ~12.2 GB VRAM. Mac Studio M2 Ultra 64GB has 46.1 GB. With Q4_K_M quantization, expect ~84 tok/s.

Runtime: llama.cppCapacity: RoomyBandwidth: HighStack: StandardBottleneck: Balanced

Operating mode

Choose the run profile you care about

Interactive favors responsiveness, while light API and scale-out lean harder on serving readiness. The fit stays the same, but the recommendation lens changes.

Current mode

Balanced

Balanced for general local use. Keeps the ranking neutral across personal and serving workflows.

Capabilities:

Select quantization to explore

Q4_K_M (Medium quality) — 12.2 GB, 84.0 tok/s, Runs well

12.2 GB required46.1 GB available

26% VRAM used

Fit status

Runs well

Decode

84.0 tok/s

TTFT

2305 ms

Safe context

788K

Memory

12.2 GB / 46.1 GB

Memory breakdown

Weights3.7 GB

KV Cache0.7 GB

Runtime0.9 GB

Headroom6.9 GB

See how fast it feels

See how fast it feelsstablelm 2 zephyr 1 6b on Mac Studio M2 Ultra 64GB
1st promptCold start — includes initialization
>What is local AI inference?
Local AI inference means running an AI language model directly on your own hardware — your laptop, desktop, or server — instead of sending requests to a remote cloud API.

When you run inference locally the model weights are loaded into your GPU or unified memory. Each token you generate requires reading those weights from memory, so memory bandwidth is the main bottleneck for decode speed.

Key benefits of running locally:
  - Full privacy: your prompts never leave your machine
  - No per-token cost or rate limits
  - Works offline once the model is downloaded
  - Latency depends only on your hardware
2nd promptWarm — model ready, no init overhead
>How much VRAM do I need?
It depends on the model size and quantization level. A rough rule of thumb:

  Model size     Q4 (4-bit)    Q8 (8-bit)    FP16
  7B params      ~4.3 GB       ~7.5 GB       ~14 GB
  13B params     ~7.9 GB       ~13.9 GB      ~26 GB
  70B params     ~42.7 GB      ~74.9 GB      ~140 GB

Most people use 4-bit quantization (Q4_K_M) which gives 90-95% of full quality at a fraction of the memory. A 24 GB GPU can comfortably run most 7B-13B models.
Estimated: 84.0 tok/s decode · 2.3s TTFT (warm) · 210 tok/s prefill

What limits this setup

This setup is broadly balanced for this model.

Shared-memory contention still exists

The OS, browser, and inference runtime all compete for the same physical memory pool, so real-world headroom is less forgiving than raw capacity suggests.

Best improvement path

Performance by workload

Workload	Grade	Fit	Decode	TTFT	Context
Chat	C	Runs well	84.0 tok/s	1257 ms	788K
Coding	C	Runs well	84.0 tok/s	2305 ms	788K
Agentic Coding	C	Runs well	84.0 tok/s	3352 ms	788K
Reasoning	C	Runs well	84.0 tok/s	2724 ms	788K
RAG	C	Runs well	84.0 tok/s	4190 ms	788K

Quantization options

How stablelm 2 zephyr 1 6b (6B params) fits at each quantization level on Mac Studio M2 Ultra 64GB (46.1 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_K	2	2.3 GB	Low	C41
Q3_K_S	3	2.9 GB	Low	C42
NVFP4	4

Get started

Copy-paste commands to run stablelm 2 zephyr 1 6b on your machine.

Run

lms load hf-stabilityai--stablelm-2-zephyr-1-6b && lms server start

Frequently asked questions

Can Mac Studio M2 Ultra 64GB run stablelm 2 zephyr 1 6b?

Yes, Mac Studio M2 Ultra 64GB can run stablelm 2 zephyr 1 6b with a C grade (Runs well). Expected decode speed: 84.0 tok/s.

How much VRAM does stablelm 2 zephyr 1 6b need?

stablelm 2 zephyr 1 6b (6B parameters) requires approximately 12.2 GB of memory with Q4_K_M quantization.

What is the best quantization for stablelm 2 zephyr 1 6b?

The recommended quantization for stablelm 2 zephyr 1 6b is Q4_K_M, which balances quality and memory efficiency.

What speed will stablelm 2 zephyr 1 6b run at on Mac Studio M2 Ultra 64GB?

On Mac Studio M2 Ultra 64GB, stablelm 2 zephyr 1 6b achieves approximately 84.0 tokens per second decode speed with a time-to-first-token of 2305ms using Q4_K_M quantization.

Can Mac Studio M2 Ultra 64GB run stablelm 2 zephyr 1 6b for coding?

For coding workloads, stablelm 2 zephyr 1 6b on Mac Studio M2 Ultra 64GB receives a C grade with 84.0 tok/s and 788K context.

What context window can stablelm 2 zephyr 1 6b use on Mac Studio M2 Ultra 64GB?

On Mac Studio M2 Ultra 64GB, stablelm 2 zephyr 1 6b can safely use up to 788K tokens of context. The model's official context limit is —, but available memory constrains the safe maximum.

See all results for Mac Studio M2 Ultra 64GB See all hardware for stablelm 2 zephyr 1 6b

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