Nice! found a CPU miner for X11 on Core2 Quad Q6600:
Do you know if CPU miners are profitable with X11 due to lower power usage or are you just experimenting for the heck of it?
Here is some math I did a while ago for an i7-4771. Older CPUs lacking AVX/AES instruction sets will perform a lot worse.
Hashrate using all 8 cores: ~0.3 MH/s
Power consumption: ~70W, 1.68 kWh per day
Cost per MH/s per day at 0.1 USD per kWh: 0.56 USD
Now if you look at Waffle's recent X11 profitability, it's around 0.0007 BTC (I hope I got the zeros right) or 0.45 USD per day.
To break even you'd need to earn > 0.0009 BTC per MH/s, or have access to < 0.08 USD/kWh electricity.
EDIT: just to emphasize the scale: even if you had free energy you'd be making 15 cents per day on a $300 CPU.