Running it on a Macbook Pro M5 48GB:

        -hf unsloth/Qwen3.6-27B-GGUF:UD-Q6_K_XL \ 
        -c 128000 \
        --parallel 1 \
        --flash-attn on \
        --no-context-shift \
        --cache-type-k q8_0 \
        --cache-type-v q8_0 \
        --temp 0.6 \
        --top-p 0.95 \
        --top-k 20 \
        --min-p 0.0 \
        --presence_penalty 0.0 \
        --reasoning on \
        --jinja \
        --chat-template-kwargs "{\"preserve_thinking\": true}" \
        --spec-type ngram-simple \
        --draft-max 64 \
        --timeout 1800

I haven't honestly dug around to figure out if there's a hardware reason for it, but prompt processing has always been a lot slower for me on macs in general. I mostly use MLX on my 24GB M4 Pro though, so I will pull llama.cpp on it as well to see what the prefill is like.

I've gotten around 16 t/s gen with 4bit and mxfp4 on that model for generation. The 3090 I mentioned has a little over 900 gb/s, while those macs i think are around 270 GB/s. If my understanding is correct, macs do utilize the bandwidth better in this case, but it still doesn't make up the difference (on the 3090 it's around 30-35 t/s depending on size of ctx).

Also, do run a quick experiment removing the cache quants if you want to tinker with it a bit more, iirc KV quant does add a small overhead during prefill.

I would be very interested to know your prefill and generation numbers.

https://github.com/jundot/omlx

note: 27b is going to be slow; use the 35b MoE if you want decent token/sec speed.