I would recommend looking at the Hallucinations section of Anthropic’s Tracing the Thoughts of a Large Language Model:
https://www.anthropic.com/research/tracing-thoughts-language-model
They found that Claude has a refusal/”I don’t know” circuit that is activated by default, and gets deactivated by a “known entities” feature when knowledge is found.
They hypothesize that hallucinations are often caused by faulty suppression of this circuit.
Can we use similar methods to estimate the size and active parameters of GPT-4.5?
Naively extrapolating from the 1800B-A280B estimate for GPT-4 and the fact that GPT4.5 costs about 2.5x as much, we get 4500B-A700B.
I have no idea if that’s a good guess, but hopefully someone can come up with a better one.