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Unformatted text preview: r can choose to either resume the currently executing process or to switch to a different process. This interval must be set short enough to ensure that the processor will switch between tasks often enough to provide the illusion of performing many tasks simultaneously. On the other hand, switching from one process to another requires thousands of clock cycles to save the state of the current process and to set up the state for the next, and hence setting the interval too short would cause poor performance. Typical timer intervals range between 1 and 10 milliseconds, depending on the processor and how it is conﬁgured. Figure 9.2(a) illustrates the system’s perspective of a hypothetical 150 ms of operation on a system with a 10 ms timer interval. During this period there are two active processes: A and B. The processor alternately executes part of process A, then part of B, and so on. As it executes these processes, it operates either in user mode, executing the instructions of the application program; or in kernel mode, performing operating system functions o...
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- Spring '10
- The American