I dont have strong servers, but I have some i7 CPU to do mining. 
So I liked the concept of ROI coin-CPU mining only, May be I mine less 3000 coins per month, but If I term deposit it for 1-12 Month. I will get 600% more coins on my 3000 Coins. 1 ROI=88 sat not bad deal for CPU.  https://roi-coin.com

I joined their community, where development showed how to increase the efficiency of CPU. Good ideas. https://discord.gg/NKn2Ngn