r/LocalLLaMA reverse-engineered the Qwen4 n-gram architecture, and RAM is the only viable tier.

A 217-upvote writeup breaks down Qwen4Exp: a router picks experts late in the layer with a large payload, so experts resist offload, while an n-gram table is a hash lookup known early and cheap to fetch. The author concludes roughly 25% of weights can move to n-gram before the tradeoff inverts, turning a 176B model into 125B in RAM plus 51B elsewhere (r/LocalLLaMA). The thread's correction to the original SSD claim is the operational detail: the n-gram index is hashed, so access is random and RAM is the only tier that works.