Thanks, I see now, OP's asking about mines, not necessarily miners (though I guess it's a bit hard to distinguish... if I mine, do I have a mine? how many cores

Thanks, I see now, OP's asking about mines, not necessarily miners (though I guess it's a bit hard to distinguish... if I mine, do I have a mine? how many cores should I have to qualify that as a mine?) Anyway, on the >50% attack, I'm not totally in agreement. The attack can drop transactions, but can't forge any (which, btw, goes towards the "there won't be transactions"). If the network would ever restart, it will be eventually verified.