Can StarCoder 15B run on Mac Studio M3 Ultra 256GB?

Q: Is unified memory on Mac Studio M3 Ultra 256GB as fast as VRAM for StarCoder 15B?

Not always. Mac Studio M3 Ultra 256GB 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

A72Great

Estimated from fit model

StarCoder 15B needs ~54.3 GB VRAM. Mac Studio M3 Ultra 256GB has 184.3 GB. With Q5_K_M quantization, expect ~53 tok/s.

Runtime: OllamaCapacity: RoomyBandwidth: HighStack: BasicBottleneck: 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

Q5_K_M (High quality) — 54.3 GB, 52.6 tok/s, Runs well

54.3 GB required184.3 GB available

29% VRAM used

Fit status

Runs well

Decode

52.6 tok/s

TTFT

3681 ms

Safe context

Memory

54.3 GB / 184.3 GB

Memory breakdown

Weights10.8 GB

KV Cache14.6 GB

Runtime1.2 GB

Headroom27.6 GB

See how fast it feels

See how fast it feelsStarCoder 15B on Mac Studio M3 Ultra 256GB
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: 52.6 tok/s decode · 3.7s TTFT (warm) · 132 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	52.6 tok/s	2008 ms	8K
Coding	A	Runs well	52.6 tok/s	3681 ms	8K
Agentic Coding	A	Runs well	52.6 tok/s	5354 ms	8K
Reasoning	A	Runs well	52.6 tok/s	4350 ms	8K
RAG	A	Runs well	52.6 tok/s	6692 ms	8K

Quantization options

How StarCoder 15B (15B params) fits at each quantization level on Mac Studio M3 Ultra 256GB (184.3 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_K	2	5.9 GB	Low	B62
Q3_K_S	3	7.4 GB	Low	B62
NVFP4	4

Get started

Copy-paste commands to run StarCoder 15B on your machine.

Run

lms load starcoder && lms server start

Your hardware

More models your Mac Studio M3 Ultra 256GB can run

Model	Params	Grade	Decode	Capabilities
Devstral 2 123B Instruct	123B	S	8.1 tok/s
Qwen3-Coder 30B A3B Instruct	30.5B	S

Frequently asked questions

Can Mac Studio M3 Ultra 256GB run StarCoder 15B?

Yes, Mac Studio M3 Ultra 256GB can run StarCoder 15B with a A grade (Runs well). Expected decode speed: 52.6 tok/s.

How much VRAM does StarCoder 15B need?

StarCoder 15B (15B parameters) requires approximately 54.3 GB of memory with Q5_K_M quantization.

What is the best quantization for StarCoder 15B?

The recommended quantization for StarCoder 15B is Q5_K_M, which balances quality and memory efficiency.

What speed will StarCoder 15B run at on Mac Studio M3 Ultra 256GB?

On Mac Studio M3 Ultra 256GB, StarCoder 15B achieves approximately 52.6 tokens per second decode speed with a time-to-first-token of 3681ms using Q5_K_M quantization.

Can Mac Studio M3 Ultra 256GB run StarCoder 15B for coding?

For coding workloads, StarCoder 15B on Mac Studio M3 Ultra 256GB receives a A grade with 52.6 tok/s and 8K context.

What context window can StarCoder 15B use on Mac Studio M3 Ultra 256GB?

On Mac Studio M3 Ultra 256GB, StarCoder 15B can safely use up to 8K tokens of context. The model's official context limit is 8K, but available memory constrains the safe maximum.

Is unified memory on Mac Studio M3 Ultra 256GB as fast as VRAM for StarCoder 15B?

See all results for Mac Studio M3 Ultra 256GB See all hardware for StarCoder 15B

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