Cpu mining is worth it, when you have dual xeons on 1 mb, not less of that.
I doubt your statement, I have server 2U XEON 12 cores 24 threads and 4 months ago I mine in ETN coin and get 32ETN/day and I have free electricity but I stop mining using that because of not worth for me. moreover now price ETN is down and diff increased. so, I think mining use CPU is not worth although you have free electricity.