1 when we processing the data,we can use a small peace of fast memory to store the data what we need temporarily.
2 CPU don't need to read the peace of program in the slow main nomory.
3 caches help us store the data what we often use in the small fast memory,when we need these data,it will help us catch the data in caches.
4 caches let the computer run faster,if we don't have caches,and we don't need the fast CPU,because the speed of the system will stuck on the main memory speed.
2
1 the purpose of the interrupt is to notice the CPU change the pattern,when I/O run finished, alter the flow of execution in response to some event, it will send sigal to notice CPU.
2 An interrupt is triggered in hardware and a trap is triggered in software.
3 User programs can generate traps intentionally. They may want to interact with some I/O which requires a system call.
3
1 CPU and device controllers all use a common bus for communication
2 A device controller is a part of a computer system that makes sense of the signals going to, and coming from the CPU.The CPU sends signals to control the other parts of the computer, is an electronic machine that works on a list of things to do.
4
1. It saves the CPU state and invokes the appropriate interrupt handler using the interrupt vector (addresses of OS routines to handle various events)
2. Handler must save and restore software state (e.g., registers it will modify)