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.
a. Assume that interrupt processing takes about 100 s (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 8 s 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 2 s. Determine what fraction of processor time is consumed
by this I/O device in this case.
