Can GPT-OSS 20B run on RTX 4000 Ada Laptop 12GB?

Q: What should I upgrade first if GPT-OSS 20B feels slow on RTX 4000 Ada Laptop 12GB?

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.

YES — With Q2_K

A81Great

Estimated from fit model

GPT-OSS 20B needs ~13.0 GB VRAM. RTX 4000 Ada Laptop 12GB has 12.0 GB. With Q2_K quantization, expect ~51 tok/s.

Runtime: OllamaCapacity: OffloadBandwidth: LowStack: BasicBottleneck: 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.

GPT-OSS 20B at Q4_K_M needs 17.7 GB — too much for RTX 4000 Ada Laptop 12GB (12.0 GB). Runs at Q2_K (13.0 GB) with low quality.

Capabilities:

Select quantization to explore

Q4_K_M (Medium quality) — 17.7 GB, exceeds 12.0 GB available

17.7 GB required12.0 GB available

148% VRAM needed

5.7 GB over capacity — needs offload or smaller quantization

Fit status

Too heavy

Decode

20.2 tok/s

TTFT

9607 ms

Safe context

Memory

17.7 GB / 12.0 GB

Offload

30%

Memory breakdown

Weights12.8 GB

KV Cache2.4 GB

Runtime1.2 GB

Headroom1.2 GB

See how fast it feels

With memory offload — actual speed may be lower

See how fast it feelsGPT-OSS 20B on RTX 4000 Ada Laptop 12GB
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: 20.2 tok/s decode · 9.6s TTFT (warm) · 50 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.

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 0.6 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	F	Too heavy	23.4 tok/s	4507 ms	4K
Coding	F	Too heavy	20.2 tok/s	9607 ms	4K
Agentic Coding	F	Too heavy	15.3 tok/s	18355 ms	4K
Reasoning	F	Too heavy	18.7 tok/s	12205 ms	4K
RAG	F	Too heavy	15.3 tok/s	22944 ms	4K

Quantization options

How GPT-OSS 20B (21B params) fits at each quantization level on RTX 4000 Ada Laptop 12GB (12.0 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_KBest for your GPU	2	8.2 GB	Low	S90
Q3_K_S	3	10.3 GB	Low	F0

Get started

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

Run

ollama run gpt-oss

Upgrade options

Hardware that runs GPT-OSS 20B well

RTX 5060 Ti 16GBBest value

16 GB VRAM (+4)448 GB/s (+16)

Makes the model fit on the accelerator instead of staying completely out of reach.31.9 tok/s decode

Makes the model fit on the accelerator instead of staying completely out of reach.

Raises estimated decode speed by about 58%.

~$449 MSRP

RTX 4060 Ti 16GBNVIDIA upgrade

16 GB VRAM (+4)

Makes the model fit on the accelerator instead of staying completely out of reach.23.5 tok/s decode

Makes the model fit on the accelerator instead of staying completely out of reach.

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

~$499 MSRP

RTX 4000 Ada 20GBBudget pick

20 GB VRAM (+8)

Makes the model fit on the accelerator instead of staying completely out of reach.53.9 tok/s decode

Makes the model fit on the accelerator instead of staying completely out of reach.

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

~$1,250 MSRP

Frequently asked questions

Can RTX 4000 Ada Laptop 12GB run GPT-OSS 20B?

Yes, RTX 4000 Ada Laptop 12GB can run GPT-OSS 20B at Q2_K quantization (Very compromised (needs ~0.6 GB host RAM)). The recommended Q4_K_M requires 17.7 GB which exceeds available memory, but at Q2_K it needs only 13.0 GB. Expected decode speed: 50.7 tok/s.

How much VRAM does GPT-OSS 20B need?

GPT-OSS 20B (21B parameters) requires approximately 17.7 GB at Q4_K_M quantization. On RTX 4000 Ada Laptop 12GB, it fits at Q2_K using 13.0 GB.

What is the best quantization for GPT-OSS 20B?

The recommended quantization is Q4_K_M, but on RTX 4000 Ada Laptop 12GB the best fitting quantization is Q2_K, which uses 13.0 GB.

What speed will GPT-OSS 20B run at on RTX 4000 Ada Laptop 12GB?

On RTX 4000 Ada Laptop 12GB, GPT-OSS 20B achieves approximately 50.7 tokens per second decode speed with a time-to-first-token of 3815ms using Q2_K quantization.

Can RTX 4000 Ada Laptop 12GB run GPT-OSS 20B for coding?

For coding workloads, GPT-OSS 20B on RTX 4000 Ada Laptop 12GB receives a F grade with 20.2 tok/s and 4K context.

What context window can GPT-OSS 20B use on RTX 4000 Ada Laptop 12GB?

On RTX 4000 Ada Laptop 12GB, GPT-OSS 20B can safely use up to 9K tokens of context at Q2_K quantization. The model's official context limit is 128K, but available memory constrains the safe maximum.

See all results for RTX 4000 Ada Laptop 12GB See all hardware for GPT-OSS 20B

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