Running three Qwen3.5 122B sessions on one Mac Studio with an on-disk KV cache
A Reddit user reportedly ran three concurrent Qwen3.5 122B sessions on a single Mac Studio, serving over 93% of prompt tokens from an on-disk KV cache instead of recomputing on GPU.
Someone on r/LocalLLaMA is reportedly running three concurrent Qwen3.5 122B sessions on a single Mac Studio, and the numbers they posted are worth paying attention to: across a 20-minute test window, 93.8% of prompt tokens were reportedly served from an on-disk KV cache, meaning the GPU only had to recompute a small fraction of what would otherwise be a full prefill every time. According to the digest, that works out to roughly one GPU’s worth of compute shared across three simultaneous chats.
The on-disk KV cache angle is the interesting part here. Persisting the KV cache to fast local storage and reusing it across sessions is not new in principle, but getting it to work reliably at 122B scale on Apple Silicon, and actually measuring the hit rate, is the kind of thing that only shows up in hobbyist write-ups. If the numbers hold under scrutiny, this is a concrete technique, not a theoretical one.
I have to be upfront: the source article was unreachable, so every specific figure here (the 789K tokens, the 93.8% hit rate, the 96GB Mac Studio spec) comes from a second-hand digest and needs to be treated as unverified until someone can read the original post. The model name and the general approach check out, but I would not go reconfiguring your server stack based on unconfirmed Reddit numbers. Check the linked thread directly before you act on any of this.