Should I read Cryptonomicon before Quicksilver?
You don’t need to have read Cryptonomicon first. But I’d recommend it, weakly. If you’ve read Cryptonomicon first, you’ll recognize that So-and-so is Blah-de-blah from C’s ancestor. Sometimes this won’t be completely obvious at first meeting, either. And you’ll get a better introduction to Qwlghm, and some other details.
No, you needn’t read it first. In fact, I think I might have liked the Baroque Cycle even better (if possible) if I hadn’t read it until afterward. Or maybe, I would have liked Cryptonomicon more after. Either way, the series works on its own. If you like Quicksilver, just wait. The 2nd and 3rd books are so. much. better.