CSE 120 Lecture Notes - Lecture 14: Protected Mode, Linked List, Hash Table
6 Mar 2018
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Problems: so many different types of i/o devices! Wide range: speed, operation, data transfer units, etc. I/o instructions - instruction of the isa designed specifically for i/o. Programmed i/o - cpu is involved in moving data from cpu register to device or vice versa. Dma (direct memory address) - cpu tells device to move x amount of data to a certain data area. Initiates process, and then you take over from there. Polling - checking a register, bit, memory, if device is ready , and busy-waits otherwise. Interrupts - cpu does not explicitly check the device. Device generates an interrupt for which the cpu then handles it. Process itself might have data copied into the kernel into the buffer. Writing from process goes directly to the device! You can hold the data for the device in the kernel while waiting for pages of the process to show.
