Is unified memory on MacBook Pro M3 Max 48GB as fast as VRAM for InternLM 20B?

Not always. MacBook Pro M3 Max 48GB 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 InternLM 20B run on MacBook Pro M3 Max 48GB?

Q: What should I upgrade first if InternLM 20B feels slow on MacBook Pro M3 Max 48GB?

Remove offload with more accelerator memory. Prioritize a GPU or unified-memory tier that fits the whole model natively. Removing offload usually helps more than small compute gains.

BARELY — Tight on Memory

C46Usable

Estimated from fit model

InternLM 20B needs ~38.8 GB VRAM. MacBook Pro M3 Max 48GB has 34.6 GB. With Q5_K_M quantization, expect ~14 tok/s.

Runtime: llama.cppCapacity: OffloadBandwidth: LowStack: StandardBottleneck: Host offload

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) — 38.8 GB, 14.1 tok/s, Very compromised (needs ~1.6 GB host RAM)

38.8 GB required34.6 GB available

112% VRAM needed

4.2 GB over capacity — needs offload or smaller quantization

Fit status

Very compromised (needs ~1.6 GB host RAM)

Decode

14.1 tok/s

TTFT

13721 ms

Safe context

Memory

38.8 GB / 34.6 GB

Offload

10%

Memory breakdown

Weights14.4 GB

KV Cache18.3 GB

Runtime0.9 GB

Headroom5.2 GB

See how fast it feels

See how fast it feelsInternLM 20B on MacBook Pro M3 Max 48GB
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: 14.1 tok/s decode · 13.7s TTFT (warm) · 35 tok/s prefill

What limits this setup

It fits through host-memory offload, and offload is the main reason performance drops.

CPU or host-memory offload is active

About 10% of the working set spills out of accelerator memory, which usually hurts latency and sustained decode throughput.

Very little memory headroom

You can run the model, but there is not much room left for longer context, bigger batches, extra apps, or future model updates.

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

Remove offload with more accelerator memory

Prioritize a GPU or unified-memory tier that fits the whole model natively. Removing offload usually helps more than small compute gains.

Buy headroom, not only minimum fit

A slightly larger memory tier gives you safer context growth and makes the recommendation more future-proof.

Increase host RAM if you keep offloading

This setup may need roughly 1.6 GB of extra host RAM just for the offloaded portion, before OS and other tools.

Performance by workload

Workload	Grade	Fit	Decode	TTFT	Context
Chat	B	Tight fit	17.0 tok/s	6212 ms	8K
Coding	C	Very compromised (needs ~1.6 GB host RAM)	14.1 tok/s	13721 ms	8K
Agentic Coding	F	Too heavy	8.9 tok/s	31579 ms	8K
Reasoning	C	Very compromised (needs ~1.6 GB host RAM)	14.1 tok/s	16215 ms	8K
RAG	F	Too heavy	8.9 tok/s	39473 ms

Quantization options

How InternLM 20B (20B params) fits at each quantization level on MacBook Pro M3 Max 48GB (34.6 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_K	2	7.8 GB	Low	C52
Q3_K_S	3	9.8 GB	Low	C53
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

Mac mini M4 64GBBudget pick

64 GB Unified (+16)

Removes host-memory offload, which is usually the single biggest latency and throughput win.8 tok/s decode

Removes host-memory offload, which is usually the single biggest latency and throughput win.

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

~$1,099 MSRP

MacBook Pro M4 Pro 64GBBest value

64 GB Unified (+16)

Removes host-memory offload, which is usually the single biggest latency and throughput win.19.4 tok/s decode

Removes host-memory offload, which is usually the single biggest latency and throughput win.

Raises estimated decode speed by about 38%.

~$1,599 MSRP

MacBook Pro M4 Max 96GBApple upgrade

96 GB Unified (+48)546 GB/s (+146)

Removes host-memory offload, which is usually the single biggest latency and throughput win.30.7 tok/s decode

Removes host-memory offload, which is usually the single biggest latency and throughput win.

Raises estimated decode speed by about 118%.

~$2,499 MSRP

Frequently asked questions

Can MacBook Pro M3 Max 48GB run InternLM 20B?

Yes, MacBook Pro M3 Max 48GB can run InternLM 20B with a C grade (Very compromised (needs ~1.6 GB host RAM)). Expected decode speed: 14.1 tok/s.

How much VRAM does InternLM 20B need?

InternLM 20B (20B parameters) requires approximately 38.8 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 MacBook Pro M3 Max 48GB?

On MacBook Pro M3 Max 48GB, InternLM 20B achieves approximately 14.1 tokens per second decode speed with a time-to-first-token of 13721ms using Q5_K_M quantization.

Can MacBook Pro M3 Max 48GB run InternLM 20B for coding?

For coding workloads, InternLM 20B on MacBook Pro M3 Max 48GB receives a C grade with 14.1 tok/s and 8K context.

What context window can InternLM 20B use on MacBook Pro M3 Max 48GB?

On MacBook Pro M3 Max 48GB, 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.

What should I upgrade first if InternLM 20B feels slow on MacBook Pro M3 Max 48GB?

See all results for MacBook Pro M3 Max 48GB See all hardware for InternLM 20B

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