For who said that GPU version is always better. Maybe this is the case, maybe it's not. It depends if and how much the code can be parallelized.
I'll try to see what CPU can achieve. And if it's not enough, I'll study the convenience to mix CPU and GPU, if I'll see that some algo cant be well parallelized on the GPU
Core i7-4670K gets about 410KHash/s on DRK while using around 77W
R9 290X gets about 2000KHash/s on DRK while using around 225W (?)
Clearly the GPU is faster and more efficient, but we're only looking at a different of about 40%. Unless someone can get a speedup out of the GPU miners to the point where it's more like 1000% more efficient, CPU mining should remain viable. Just my two cents. :-)
Sorry, but your assumptions are wrong. My 4 x R9 290 rig uses about 450W when idle and about 1450W when 100% busy mining scrypt coins. However when mining DRK it only uses 900W of power (so about 112W for each card) - due to the nature of calculations (lots of random memory access in 3 or 4 hash functions) full potential of GPU cores cannot be used and they use much less power. That means mining with GPU is over 300% more efficient.
Ok, but we have to compare with total wattage right?
4xR9 -> 900W/4= 225W, 2000khs/225 = 8.88 kh/sec for Watt
i7-4670k -> 77w, 410Khs/77 = 5.32 kh/sec for Watt
Surely then, it's easier a rig of GPUs than a rig of CPUs. But this for now it's a 30% improvement for Watt, depending on what CPUs and what GPUs.
So I want to see if there is a 30% margin to improve the cpu miner.
Let me know if you and the others think that I am wrong about something...