Comment by zargon
10 hours ago
Qwen3.5 series is a little bit of an exception to the general rule here. It is incredibly kv cache size efficient. I think the max context (262k) fits in 3GB at q8 iirc. I prefer to keep the cache at full precision though.
I just tested it and have to make a correction. With llama.cpp, 262144 tokens context (Q8 cache) used 8.7 GB memory with Qwen3.6 27B. Still very impressive.
The MoE variants are more cache efficient. Here from Qwen3.6 35B A3B MoE with 256k (262144) context at full F16 (so no cache quality loss):
The MXFP4-quantized variant from Unsloth just fits my 5090 with 32GB VRAM at 256k context.
Meanwhile here's for Qwen 3.6 27B:
So 16 tokens per MiB for the 27B model vs about 51 tokens per MiB for the 35B MoE model.
I went for the Q5 UD variant for 27B so could just fit 48k context, though it seems if I went for the Q4 UD variant I could get 64k context.
That said I haven't tried the Qwen3.6 35B MoE to figure out if it can effectively use the full 256k context, that varies from model to model depending on the model training.