Is Qwen3.5-4B-Base or Qwen3-8B smaller?

Qwen3.5-4B-Base is smaller at Q4_K_M: 2.52 GiB against 4.68 GiB.

Which uses less memory at long context?

Qwen3.5-4B-Base — its KV cache at 32K context is 4.5x smaller, because of how its attention layers cache.

Model comparison

Qwen3.5-4B-Base vs Qwen3-8B

At Q4_K_M, Qwen3.5-4B-Base is the smaller download — 2,708,804,608 bytes against 5,027,783,488. At long context the gap widens: Qwen3.5-4B-Base's KV cache at 32K is 4.5× smaller, which usually matters more than the difference in weights.

From the file· summed bytes, KV per layer

Side by side

	Qwen3.5-4B-Base	Qwen3-8B
Parameters	4.7B	8.2B
Architecture	qwen35	qwen3
Layers	32	36
Native context	262,144	40,960
Mixture of experts	no	no
Quantizations published	14	51
Smallest quantization	1.78 GiB	2.12 GiB
Q4_K_M	2.52 GiB	4.68 GiB
Licence	cc-by-nc-4.0	apache-2.0

KV cache by context

the term that decides long-context viability

Context	Qwen3.5-4B-Base	Qwen3-8B	Ratio
4,096	0.13 GiB	0.56 GiB	4.50×
8,192	0.25 GiB	1.13 GiB	4.50×
16,384	0.50 GiB	2.25 GiB	4.50×
32,768	1.00 GiB	4.50 GiB	4.50×
65,536	2.00 GiB	9.00 GiB	4.50×
131,072	4.00 GiB	18.00 GiB	4.50×