All of the stream processors operate in parallel, and while their individual operation is independent of one another, they are all synchronous with eachother. This means that they all share the same common clock, so in this case, each of the individual 1120 stream processors operates at 915 MHz.
While this is similar to having multiple cores in a CPU, it is not entirely the same thing. Each stream processor is controlled together by the main GPU, which directs how the data in each stream is to be handled all-at-one (similar to the way SIMD instructions are handled on a CPU).