The A8-3870K is very similar to the A8-3850 in price and specifications. It costs only USD 5 more than the A8-3850 and has almost the same clock rate (3 GHz vs. 2.9 GHz), but has a far better overclocking potential, thanks to its unlocked clock multiplier.
As the A8-3850, the A8-3870K has the best integrated video solution we’ve seen so far, beating its competitors from Intel really hard.
Also on the good side, applications that perform better with four “real” cores will perform better on the A8-3870K and A8-3850 than on the Core i3-2100 and Core i3-2105, which have only two “real” cores and two “simulated” ones, using Hyper-Threading technology.
The bad news is that aside from gaming, 3D rendering, and overclocking, the Core i3-2100 and Core i3-2105 are faster and, depending on the application, by a large margin. They also cost less.
So, if you are a gamer or an overclocker on a really tight budget, the new A8-3870K is a really nice option. But if you are an average user who won’t play games, the Core i3-2105 and the Core i3-2100 are far better options.