Can Gemma 3 12B run on Mac Studio M2 Ultra 128GB?

Q: Is unified memory on Mac Studio M2 Ultra 128GB as fast as VRAM for Gemma 3 12B?

Not always. Mac Studio M2 Ultra 128GB 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.

YES — Runs Great

A76Great

Estimated from fit model

Gemma 3 12B needs ~26.9 GB VRAM. Mac Studio M2 Ultra 128GB has 92.2 GB. With Q4_K_M quantization, expect ~50 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) — 26.9 GB, 50.4 tok/s, Runs well

26.9 GB required92.2 GB available

29% VRAM used

Fit status

Runs well

Decode

50.4 tok/s

TTFT

3838 ms

Safe context

131K

Memory

26.9 GB / 92.2 GB

Memory breakdown

Weights7.3 GB

KV Cache4.9 GB

Runtime0.9 GB

Headroom13.8 GB

See how fast it feels

See how fast it feelsGemma 3 12B on Mac Studio M2 Ultra 128GB
1st promptCold start — includes initialization
>Write a Python function to sort a list
Here's a Python function that sorts a list using quicksort:

def quicksort(arr):
    if len(arr) <= 1:
        return arr
    pivot = arr[len(arr) // 2]
    left   = [x for x in arr if x < pivot]
    middle = [x for x in arr if x == pivot]
    right  = [x for x in arr if x > pivot]
    return quicksort(left) + middle + quicksort(right)

# Example usage
numbers = [3, 6, 8, 10, 1, 2, 1]
print(quicksort(numbers))  # [1, 1, 2, 3, 6, 8, 10]

The algorithm picks a pivot, partitions the list into smaller, equal, and larger elements, then recursively sorts each partition and concatenates the results.
2nd promptWarm — model ready, no init overhead
>Now add type hints and a docstring
def quicksort(arr: list[int]) -> list[int]:
    """Sort a list using the quicksort algorithm.

    Args:
        arr: List of integers to sort.

    Returns:
        A new sorted list.
    """
    if len(arr) <= 1:
        return arr
    pivot = arr[len(arr) // 2]
    left   = [x for x in arr if x < pivot]
    middle = [x for x in arr if x == pivot]
    right  = [x for x in arr if x > pivot]
    return quicksort(left) + middle + quicksort(right)

Added type hints for the input and return type, plus a Google-style docstring.
Estimated: 50.4 tok/s decode · 3.8s TTFT (warm) · 126 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	A	Runs well	50.4 tok/s	2094 ms	131K
Coding	A	Runs well	50.4 tok/s	3838 ms	131K
Agentic Coding	A	Runs well	50.4 tok/s	5583 ms	131K
Reasoning	A	Runs well	50.4 tok/s	4536 ms	131K
RAG	A	Runs well	50.4 tok/s	6978 ms	131K

Quantization options

How Gemma 3 12B (12B params) fits at each quantization level on Mac Studio M2 Ultra 128GB (92.2 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_K	2	4.7 GB	Low	B69
Q3_K_S	3	5.9 GB	Low	B69
NVFP4	4

Get started

Copy-paste commands to run Gemma 3 12B on your machine.

Run

ollama run gemma3:12b

Your hardware

More models your Mac Studio M2 Ultra 128GB can run

Model	Params	Grade	Decode	Capabilities
Devstral 2 123B Instruct	123B	S	6.3 tok/s
Qwen3-Coder 30B A3B Instruct	30.5B	S

Frequently asked questions

Can Mac Studio M2 Ultra 128GB run Gemma 3 12B?

Yes, Mac Studio M2 Ultra 128GB can run Gemma 3 12B with a A grade (Runs well). Expected decode speed: 50.4 tok/s.

How much VRAM does Gemma 3 12B need?

Gemma 3 12B (12B parameters) requires approximately 26.9 GB of memory with Q4_K_M quantization.

What is the best quantization for Gemma 3 12B?

The recommended quantization for Gemma 3 12B is Q4_K_M, which balances quality and memory efficiency.

What speed will Gemma 3 12B run at on Mac Studio M2 Ultra 128GB?

On Mac Studio M2 Ultra 128GB, Gemma 3 12B achieves approximately 50.4 tokens per second decode speed with a time-to-first-token of 3838ms using Q4_K_M quantization.

Can Mac Studio M2 Ultra 128GB run Gemma 3 12B for coding?

For coding workloads, Gemma 3 12B on Mac Studio M2 Ultra 128GB receives a A grade with 50.4 tok/s and 131K context.

What context window can Gemma 3 12B use on Mac Studio M2 Ultra 128GB?

On Mac Studio M2 Ultra 128GB, Gemma 3 12B can safely use up to 131K tokens of context. The model's official context limit is 131K, but available memory constrains the safe maximum.

Is unified memory on Mac Studio M2 Ultra 128GB as fast as VRAM for Gemma 3 12B?

See all results for Mac Studio M2 Ultra 128GB See all hardware for Gemma 3 12B

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