Wait so does it compute anything or does it store something? In either case, you can only squeeze so much information into a certain amount of space (or to be more precise, enclose it in a minimal surface area), with black holes being the upper limit.
And i still don't get what's (simply put) special about rotation/oscillation not requiring energy.
Also keep in mind that for crystals, the atoms aren't
forced to stay where they are, grid places are just better energy-wise (without interstitials, steel would be pretty brittle). Likewise, assuming time to actually become discrete is probably a fallacy. My interpretations here might be wonky, so please reply to the first point before commenting on this part.