> For example, there is no add-with-carry, nor a convenient way to get the carry-out at a low level. IIUC, you're supposed to break the bignum up into (say) 56

> For example, there is no add-with-carry, nor a convenient way to get the carry-out at a low level. IIUC, you're supposed to break the bignum up into (say) 56-bit chunks, and use the upper bits of the register as the carry. I'm sceptical that that works as well as it should for practical bignum applications, though. (I haven't had occasion to try it out.)