There are two common ways to make them "ASIC resistant" A CPU can do a lot of things while the mining ASIC's are focused on just the one calculation. So the two common ways are. The asic has an advantage because it will be far far smaller than a full CPU or GPU since it only contains the bare minimum logic to do the calculation. The first way is to require huge amounts of memory to do the calculation. You can't fake out the memory, you just need it on the die. This reduces the size that can be saved by creating a custom ASIC. An interesting twist on this is there are some coins now with an increasing memory requirement. Ie, right now it might require 500 meg memory but each time the difficulty hits certain points the memory requirement of the calculation doubles. So now not only does the ASIC have to be larger, eventually it will be unable to do the calculation unless it keeps memory of modern GPU's. Second one is to make the algorithm harder. Bitcoin is so susceptible since SHA-256 is a single calculation. There are coins out there now with 11 or 13 or even 15 different calclations required for a single block. Now you have to design an ASIC that can solve 15 different algorithms and maybe even has the memory requirements above. Now the ASIC is far harder to design and once you do design it the performance gains are far less than the were. I think for bitcoin the hash/watt increase by ASIC's was something like 100x better. (speculation, I think i read that) Then the Scrypt ASIC's was much lower. On the order of 10-20x. X11 and beyond algorithms would be even lower. And then the ASIC's have to overcome the inherent disadvantage of process. Ie, none of the ASIC designers are paying the enormous costs involved in trying to get their chips onto bleeding edge processes. I think the best ones are at 28nm in the near future, while most of the fabs are currently working on processes in the 14-20nm range and those cost far more money and may not make sense at the volumes they build their ASIC's. Ie, 100,000 chips not 10 million of chips. Of course there are literally hundreds of altcoins now and the pump n dump has really hit credibility. Some of the ones I mine have lost 60% of their value recently. I just do it on a small scale for the learning though. I probably barely pay for the power I use.