Consider a system employing interrupt-driven I/O for a particular device that transfers data at an average of 8 KB/s on a continuous basis. Required:
a. Assume that interrupt processing takes about 100μs (i. e., the time to jump to the interrupt service routine (ISR), execute it, and return to the main program). Determine what fraction of processor time is consumed by this I/O device if it interrupts for every byte.
b. Now assume that the device has two 16-byte buffers and interrupts the processor when one of the buffers is full. Naturally, interrupt processing takes longer, because the ISR must transfer 16 bytes. While executing the ISR, the processor takes about 8μs for the transfer of each byte. Determine what fraction of processor time is consumed by this I/O device in this case.
c. Now assume that the processor is equipped with a block transfer I/O instruction such as that found on the Z8000. This permits the associated ISR to transfer each byte of a block in only 2μs. Determine what fraction of processor time is consumed by this I/O device in this case.