If you're going to be using UE4, you absolutely must have a quad core processor which runs very fast. I recommend an intel i7. There is no exceptions. UE4 compiles shaders in the background and it uses your other processor cores to do this while you're using the editor. If you don't have enough cores, you WILL have to wait for the shaders to finish compiling. This can take up to two minutes to complete. Every time you move an object around in your scene, it also causes a shader recompile. So, you'll be moving something, waiting two minutes, moving it again, waiting two minutes, etc. UE4 is unusable without enough cores. If your time is worth anything, get a powerful processor!