Can InternLM 20B run on Mac Studio M2 Ultra 64GB?

Q: Is unified memory on Mac Studio M2 Ultra 64GB as fast as VRAM for InternLM 20B?

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.

YES — Tight Fit

B58Good

Estimated from fit model

InternLM 20B needs ~40.5 GB VRAM. Mac Studio M2 Ultra 64GB has 46.1 GB. With Q5_K_M quantization, expect ~33 tok/s.

Runtime: llama.cppCapacity: TightBandwidth: 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

Q5_K_M (High quality) — 40.5 GB, 32.9 tok/s, Tight fit

40.5 GB required46.1 GB available

88% VRAM used

Fit status

Tight fit

Decode

32.9 tok/s

TTFT

5890 ms

Safe context

Memory

40.5 GB / 46.1 GB

Memory breakdown

Weights14.4 GB

KV Cache18.3 GB

Runtime0.9 GB

Headroom6.9 GB

See how fast it feels

See how fast it feelsInternLM 20B on Mac Studio M2 Ultra 64GB
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: 32.9 tok/s decode · 5.9s TTFT (warm) · 82 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	B	Runs well	32.9 tok/s	3213 ms	8K
Coding	B	Tight fit	32.9 tok/s	5890 ms	8K
Agentic Coding	F	Too heavy	23.2 tok/s	12141 ms	8K
Reasoning	B	Tight fit	32.9 tok/s	6961 ms	8K
RAG	F	Too heavy	23.2 tok/s	15176 ms	8K

Quantization options

How InternLM 20B (20B params) fits at each quantization level on Mac Studio M2 Ultra 64GB (46.1 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_K	2	7.8 GB	Low	C50
Q3_K_S	3	9.8 GB	Low	C51
NVFP4	4

Get started

Copy-paste commands to run InternLM 20B on your machine.

Run

docker run --rm -it ghcr.io/ggerganov/llama.cpp:full \
  --hf-repo "internlm/internlm2_5-20b-chat" \
  --hf-file "internlm2_5-20b-chat-Q5_K_M.gguf" \
  -c 4096 -ngl 99

Upgrade options

Hardware that runs InternLM 20B well

MacBook Pro M4 Max 96GBBudget pick

96 GB Unified (+32)

Adds memory headroom for longer context windows and future model growth.30.7 tok/s decode

Adds memory headroom for longer context windows and future model growth.

~$2,499 MSRP

Mac Studio M3 Ultra 96GBBest value

96 GB Unified (+32)819 GB/s (+19)

Adds memory headroom for longer context windows and future model growth.39.4 tok/s decode

Adds memory headroom for longer context windows and future model growth.

~$3,999 MSRP

Frequently asked questions

Can Mac Studio M2 Ultra 64GB run InternLM 20B?

Yes, Mac Studio M2 Ultra 64GB can run InternLM 20B with a B grade (Tight fit). Expected decode speed: 32.9 tok/s.

How much VRAM does InternLM 20B need?

InternLM 20B (20B parameters) requires approximately 40.5 GB of memory with Q5_K_M quantization.

What is the best quantization for InternLM 20B?

The recommended quantization for InternLM 20B is Q5_K_M, which balances quality and memory efficiency.

What speed will InternLM 20B run at on Mac Studio M2 Ultra 64GB?

On Mac Studio M2 Ultra 64GB, InternLM 20B achieves approximately 32.9 tokens per second decode speed with a time-to-first-token of 5890ms using Q5_K_M quantization.

Can Mac Studio M2 Ultra 64GB run InternLM 20B for coding?

For coding workloads, InternLM 20B on Mac Studio M2 Ultra 64GB receives a B grade with 32.9 tok/s and 8K context.

What context window can InternLM 20B use on Mac Studio M2 Ultra 64GB?

On Mac Studio M2 Ultra 64GB, InternLM 20B 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 M2 Ultra 64GB as fast as VRAM for InternLM 20B?

See all results for Mac Studio M2 Ultra 64GB See all hardware for InternLM 20B

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