One of the engineering challenges with large SMP server designs is to maintain near-linear scalability as the number of CPUs increases.
HiperDispatch helps address the problem through a combination of hardware features, z/OS dispatching, and the z/OS Workload Manager.
In a large SMP design such as IBM Z, some CPUs are physically "closer" with faster access to cache memory that might hold supporting data for particular tasks.
HiperDispatch exploits this fact and steers tasks to the CPUs most likely to have the fastest access to relevant data already in cache.
If z/OS Workload Manager senses that there's a risk the pending task will miss its service level (responding within a certain number of milliseconds to a user request for example), Workload Manager and HiperDispatch will send the task over to an idle CPU for processing, even if that CPU must fetch data from slower main memory.