Diagram C in Figure 3-1 is extremely unfortunate and will likely be reported to the operating system vendor. It does happen, although rarely. In this situation, for some reason, the next process waiting in the queue cannot be assigned to either of the idle servers (think CPUs). There is a serialization issue, and parallelism is being thwarted.

While technical people don't usually think of it this way, it's an interesting human characteristic to desire parallelization. Anyone driving on a busy road instinctively knows that adding lanes will speed up traffic. Most people are not aware of it, but such a solution increases parallelism-allowing more work to be done in a given period of time.

When businesspeople can't find a single computer to run their business on, they will ask, "Can we run each division on its own computer?" Without knowing it, they are asking if they can parallelize their divisions' IT operations.