Trapped by a metaphor... a mind is like a computer, but a mind is not a computer. If you build a fast computer model of a mind, then you have - wait for it! - a fast computer model of a mind!

Sentience is more than just a matter of modelling, surely?

Note, I did not say that a sentient, non-human thinking being is an impossibility, but I am not sure that it would happen by building big fast models.