Token generation is nominally bandwidth limited. Prefill/prompt processing is nominally compute limited.

For CPU inference on old hardware I don't think q4 offers any benefit over q8 since the AVX unit doesn't support such small floats. I don't even think AVX supports 4-bit int math. IIRC AVX2 does.

Such a system is RAM bandwidth limited and not compute limited Switching to q4 from q8 would decrease the amount of data needing to be loaded by half. The token generation rate would nearly double. But generally if you can do q6 or q8 and you have enough RAM you really should. Even if it's slower.