Can Qwen 3.5 27B run on RX 6800 16GB?

Q: What should I upgrade first if Qwen 3.5 27B feels slow on RX 6800 16GB?

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 Q3_K_S

A74Great

Estimated from fit model

Qwen 3.5 27B needs ~18.9 GB VRAM. RX 6800 16GB has 16.0 GB. With Q3_K_S quantization, expect ~11 tok/s.

Runtime: llama.cppCapacity: OffloadBandwidth: MediumStack: 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.

Qwen 3.5 27B at Q4_K_M needs 22.1 GB — too much for RX 6800 16GB (16.0 GB). Runs at Q3_K_S (18.9 GB) with low quality. 2 quantization levels fit.

Capabilities:

Select quantization to explore

Q4_K_M (Medium quality) — 22.1 GB, exceeds 16.0 GB available

22.1 GB required16.0 GB available

138% VRAM needed

6.1 GB over capacity — needs offload or smaller quantization

Fit status

Too heavy

Decode

7.0 tok/s

TTFT

27705 ms

Safe context

Memory

22.1 GB / 16.0 GB

Offload

30%

Memory breakdown

Weights16.5 GB

KV Cache3.2 GB

Runtime0.9 GB

Headroom1.6 GB

See how fast it feels

With memory offload — actual speed may be lower

See how fast it feelsQwen 3.5 27B on RX 6800 16GB
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: 7.0 tok/s decode · 27.7s TTFT (warm) · 18 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 20% 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 2.0 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	8.2 tok/s	12922 ms	4K
Coding	F	Too heavy	7.0 tok/s	27705 ms	4K
Agentic Coding	F	Too heavy	5.3 tok/s	53425 ms	4K
Reasoning	F	Too heavy	7.0 tok/s	32743 ms	4K
RAG	F	Too heavy	5.3 tok/s	66781 ms	4K

Quantization options

How Qwen 3.5 27B (27B params) fits at each quantization level on RX 6800 16GB (16.0 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_KBest for your GPU	2	10.5 GB	Low	S93
Q3_K_S	3	13.2 GB	Low	F0

Get started

Copy-paste commands to run Qwen 3.5 27B on your machine.

Run

ollama run qwen3.5:27b

Upgrade options

Hardware that runs Qwen 3.5 27B well

RX 7900 XT 20GBBest value

20 GB VRAM (+4)800 GB/s (+288)

Makes the model fit on the accelerator instead of staying completely out of reach.18.3 tok/s decode

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

Raises estimated decode speed by about 161%.

~$899 MSRP

RX 7900 XTX 24GBBudget pick

24 GB VRAM (+8)960 GB/s (+448)

Makes the model fit on the accelerator instead of staying completely out of reach.45.3 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.

~$999 MSRP

Radeon AI PRO R9700 32GBAMD upgrade

32 GB VRAM (+16)640 GB/s (+128)

Makes the model fit on the accelerator instead of staying completely out of reach.24.8 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.

~$1,899 MSRP

Frequently asked questions

Can RX 6800 16GB run Qwen 3.5 27B?

Yes, RX 6800 16GB can run Qwen 3.5 27B at Q3_K_S quantization (Very compromised (needs ~2 GB host RAM)). The recommended Q4_K_M requires 22.1 GB which exceeds available memory, but at Q3_K_S it needs only 18.9 GB. Expected decode speed: 11.3 tok/s.

How much VRAM does Qwen 3.5 27B need?

Qwen 3.5 27B (27B parameters) requires approximately 22.1 GB at Q4_K_M quantization. On RX 6800 16GB, it fits at Q3_K_S using 18.9 GB.

What is the best quantization for Qwen 3.5 27B?

The recommended quantization is Q4_K_M, but on RX 6800 16GB the best fitting quantization is Q3_K_S, which uses 18.9 GB.

What speed will Qwen 3.5 27B run at on RX 6800 16GB?

On RX 6800 16GB, Qwen 3.5 27B achieves approximately 11.3 tokens per second decode speed with a time-to-first-token of 17153ms using Q3_K_S quantization.

Can RX 6800 16GB run Qwen 3.5 27B for coding?

For coding workloads, Qwen 3.5 27B on RX 6800 16GB receives a F grade with 7.0 tok/s and 4K context.

What context window can Qwen 3.5 27B use on RX 6800 16GB?

On RX 6800 16GB, Qwen 3.5 27B can safely use up to 4K tokens of context at Q3_K_S quantization. The model's official context limit is 131K, but available memory constrains the safe maximum.

What should I upgrade first if Qwen 3.5 27B feels slow on RX 6800 16GB?

See all results for RX 6800 16GB See all hardware for Qwen 3.5 27B

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