Recs.
Updated
Launched in Q3 of 2015, this is a 64bit 14nm chip created by Intel. It has a 3.5 GHz base frequency and uses Intel integrated HD Graphics 530.
Specs
Pros
Pro Close performance to an i7-4790K
The performance of the i5 6660K is similar to a more expensive i7 processor in gaming situations. While the i7 does use more threading (twice as much), there are very few PC games that can actually take advantage of this making the i5 a good choice when building a gaming specific PC.
Pro Can allow for extreme gaming solutions
The chip itself allows for 16 PCIe 3.0 lanes. This translates into how many PCIe devices can be used at the same time and how fast they can be controlled which makes for a scenario where multiple PCIe GPUs can be used at their top transfer speed of 16x for one and 8x for two.
Cons
Con Does not come with a heatsink
No longer does Intel include a heatsink with their new CPUs, so the user will have to purchase their own. While they are not too expensive, that basically means out of the box this can not be used unless a purchase was made for a heatsink along with this item.
Con Adds another pin to the connection
This processor uses the LGA 1151 CPU socket. For those upgrading from an older generation chip this means the will need to purchase a new motherboard and possibly RAM in order to use this chip. This can be expensive to replace so many components all for a single new pin in the chips connection. While the performance will be better than the last generation, it may not be worth the price of all new gear to see this performance.