<< If it makes a chime on startup, it has found a ROM. >>

Oh yes, that's simple I should have thought about it.

<< The IIci has a jumper at W1 that enables the built-in ROM. >>

That's right, I can see the jumper.

Thanks for your answers.

I'm not confident because there's a weird (made by hand) solding on the motherboard. Seems someone already tried to fix it.