Intel Xeon Phi processors deliver a huge amount of computational power. When used efficiently, they improve application performance and shorten the time-to-solution. Our talk will describe the processor architecture and discuss on how to efficiently use the hardware resources. We will cover different mechanisms to address this efficient usage. Among the mechanisms, we will introduce QPhiX. QPhiX is a library that provides sparse solvers and slash kernels for Lattice QCD calculations and that it is optimized for Intel(R) manycore architectures.