L1 cache holds cache lines retrieved from the l2

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Unformatted text preview: emory I/O bus USB controller mouse keyboard graphics adapter monitor disk controller disk (a) The CPU initiates a disk read by writing a command, logical block number, and destination memory address to the memory-mapped address associated with the disk. CPU chip register file ALU bus interface main memory I/O bus USB controller mouse keyboard graphics adapter monitor disk controller disk (b) The disk controller reads the sector and performs a DMA transfer into main memory. CPU chip register file ALU bus interface main memory I/O bus USB controller mouse keyboard graphics adapter monitor disk controller disk (c) When the DMA transfer is complete, the disk controller notifies the CPU with an interrupt. Figure 6.12: Reading a disk sector. 292 CHAPTER 6. THE MEMORY HIERARCHY The CPU issues commands to I/O devices using a technique called memory-mapped I/O (Figure 6.12(a)). In a system with memory-mapped I/O, a block of addresses in the address space is reserved for communicating with I/O devices. Each of these addresses is known as an I/O port. Each device is associated with (or mapped to) one or more ports when it is attached to the bus. As a simple examp...
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