According to the article hendzen linked to, the Phi processors are absolutely general purpose CPUs -- they can be the main CPU on the board and can boot and run stock OSes.<p>This is much more powerful than a GPU, which is fundamentally SIMD -- it can hit TFLOPS speeds running hundreds of threads <i>doing different things</i>.  While not everyone will need this power, I suspect it will open up entire new classes of applications.