Six step process to perform DMa transfer 道讨六 传输 1. device driver is told to transfer disk data to buffer at address x CPU DMA controller transfers 2 device driver tells disk bytes to buffer X controller to transfer c increasing memory bytes from disk to buffer cache address and decreasing at address x C until C= 0 6. when C=0. DMA interrupts CPU to signal DMA/bus/interrupt -CPU memory bus controller memorybuffer transfer completion PCI bus 3. disk controller initiates DMA transfer iDE disk controller 4. disk controller send each byte to DMA controller Applied Operating System Concepts 12.7 Silberschatz, Galvin, and Gagne @199912.7 Silberschatz, Galvin, and Gagne ©1999 Applied Operating System Concepts Six step process to perform DMA transfer (通过六步来完成DMA传输)