Only one interrupt is generated per block by DMA controller rather than an

Only one interrupt is generated per block by dma

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Only one interrupt is generated per block by DMA controller, rather than an interrupt per byte.
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How a Modern Computer WorksA von Neumann architecture
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Memory ProtectionWe must protect the OS from access by user programs and protect user programs from one another.We must provide memory protection at least for the interrupt vector and the interrupt service routines of the operating system.In order to have memory protection, use two registers provided by the hardware that determine the range of legal addresses a program may access:Base register– holds the smallest legal physical memory address.Limit register– contains the size of the range Memory outside the defined range is protected.
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Use of A Base and Limit RegistersCPU must check every memory access generated in user mode to be sure it is between base and limit for that user
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Hardware Address Protection
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Operating-System Operations (cont.)The processor switches between the two modes depending on what type of code is running on the processor. Applications run in user mode, and core operating system components run in kernel mode.Dual-mode operation allows OS to protect itself and other system componentsMode bit provided by hardwareProvides ability to distinguish when system is running user code or kernel codeSome instructions designated as privileged, only executable in kernel modeSystem call changes mode to kernel, return from call resets it to user modeIf an attempt is made to execute a privileged instruction in user mode, the hardware does not execute the instruction but rather treats it as illegal and traps it to the operating system.
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Operating-System Operations (cont.)The processor switches between the two modes depending on what type of code is running on the processor. Applications run in user mode, and core operating system components run in kernel mode.Dual-mode operation allows OS to protect itself and other system componentsMode bit provided by hardwareProvides ability to distinguish when system is running user code or kernel codeSome instructions designated as privileged, only executable in kernel modeSystem call changes mode to kernel, return from call resets it to user modeIf an attempt is made to execute a privileged instruction in user mode, the hardware does not execute the instruction but rather treats it as illegal and traps it to the operating system.
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  • Fall '19
  • Interrupt, Computer data storage, Interrupt handler

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