One of the best depictions I've seen of a truly sentient machine has been in Alan Dean Foster's series Jumping Off The Planet, Bouncing Off the Moon, and Leaping to the Stars. In that near future, machines build and program other machines because they're the only ones that can grasp the insane level of complexity and deal with the computations. Once the seed programs are in place, they run and develop on their own, creating and seeking new solutions just like a human child does from the instant of birth. Only they of course live thousands of times faster than a person and can create and experience many more 'connections' than a human ever could. They're intelligent, but not very 'human' if you get my drift.