Can Qwen 3.5 4B run on GTX 1660 Ti 6GB?

Q: What should I upgrade first if Qwen 3.5 4B feels slow on GTX 1660 Ti 6GB?

Buy headroom, not only minimum fit. A slightly larger memory tier gives you safer context growth and makes the recommendation more future-proof.

YES — With Offload

S92Excellent

Estimated from fit model

Qwen 3.5 4B needs ~6.1 GB VRAM. GTX 1660 Ti 6GB has 6.0 GB. With Q4_K_M quantization, expect ~48 tok/s.

Runtime: llama.cppCapacity: OffloadBandwidth: LowStack: 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) — 6.1 GB, 48.4 tok/s, Runs with offload (needs ~0.1 GB host RAM)

6.1 GB required6.0 GB available

102% VRAM needed

100 MB over capacity — needs offload or smaller quantization

Fit status

Runs with offload (needs ~0.1 GB host RAM)

Decode

48.4 tok/s

TTFT

3997 ms

Safe context

15K

Memory

6.1 GB / 6.0 GB

Memory breakdown

Weights2.4 GB

KV Cache2.2 GB

Runtime0.9 GB

Headroom0.6 GB

See how fast it feels

See how fast it feelsQwen 3.5 4B on GTX 1660 Ti 6GB
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: 48.4 tok/s decode · 4.0s TTFT (warm) · 121 tok/s prefill

What limits this setup

This setup is broadly balanced for this model.

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.

Older PCIe generation

PCIe 3.0 is workable, but it compounds the penalty when you offload heavily or try to scale across multiple cards.

Best improvement path

Buy headroom, not only minimum fit

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

Performance by workload

Workload	Grade	Fit	Decode	TTFT	Context
Chat	S	Tight fit	56.0 tok/s	1886 ms	15K
Coding	S	Runs with offload (needs ~0.1 GB host RAM)	48.4 tok/s	3997 ms	15K
Agentic Coding	F	Too heavy	24.7 tok/s	11385 ms	15K
Reasoning	S	Runs with offload (needs ~0.1 GB host RAM)	48.4 tok/s	4724 ms	15K
RAG	F	Too heavy	24.7 tok/s	14231 ms

Quantization options

How Qwen 3.5 4B (4B params) fits at each quantization level on GTX 1660 Ti 6GB (6.0 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_K	2	1.6 GB	Low	S94
Q3_K_S	3	2.0 GB	Low	S95
NVFP4	4

Get started

Copy-paste commands to run Qwen 3.5 4B on your machine.

Run

ollama run qwen3.5:4b

Frequently asked questions

Can GTX 1660 Ti 6GB run Qwen 3.5 4B?

Yes, GTX 1660 Ti 6GB can run Qwen 3.5 4B with a S grade (Runs with offload (needs ~0.1 GB host RAM)). Expected decode speed: 48.4 tok/s.

How much VRAM does Qwen 3.5 4B need?

Qwen 3.5 4B (4B parameters) requires approximately 6.1 GB of memory with Q4_K_M quantization.

What is the best quantization for Qwen 3.5 4B?

The recommended quantization for Qwen 3.5 4B is Q4_K_M, which balances quality and memory efficiency.

What speed will Qwen 3.5 4B run at on GTX 1660 Ti 6GB?

On GTX 1660 Ti 6GB, Qwen 3.5 4B achieves approximately 48.4 tokens per second decode speed with a time-to-first-token of 3997ms using Q4_K_M quantization.

Can GTX 1660 Ti 6GB run Qwen 3.5 4B for coding?

For coding workloads, Qwen 3.5 4B on GTX 1660 Ti 6GB receives a S grade with 48.4 tok/s and 15K context.

What context window can Qwen 3.5 4B use on GTX 1660 Ti 6GB?

On GTX 1660 Ti 6GB, Qwen 3.5 4B can safely use up to 15K tokens of context. The model's official context limit is 131K, but available memory constrains the safe maximum.

What should I upgrade first if Qwen 3.5 4B feels slow on GTX 1660 Ti 6GB?

See all results for GTX 1660 Ti 6GB See all hardware for Qwen 3.5 4B

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