Yep, it's the magic smoke. A wizard casts a spell and the puff of smoke is collected and sealed in a slab. Inscriptions are added to the top for potentiating the effect, along with runes and geometric patterns on the board.
What? you thought tiny metal sandwiches made rocks think?
You run the chips too hot or too high a voltage and you'll let out the magic smoke. It should say only good as a smoke machine once, because they usually don't work anymore after you let the magic out of them.
It's also what you consider a machine. Living organisms are machines, but most of them break before reaching ignition temperature. Plus, smoke requires burning and burning requires oxygen, so no machine will smoke without O2.