Lecture 3: Machine Organization 3

Question 1

Device Controllers:

Answer 1

Hardware interface between device and bus : handles the I/O signals of the CPU (Do not confuse with device drivers which are software)

Question 2

I/O interface:

Answer 2

method used to transfer info between device and memory

Question 3

Programmed I/O:

Answer 3

I/O instructions are part of a processor program and CPU executes the instruction of the program (transferring data to memory).

Question 4

Interrupt-initiated I/O:

Answer 4

Device interrupts the CPU to transfer its data

Question 5

Direct Memory Access (DMA):

Answer 5

device had direct access to memory

no CPU involvement is necessary

Question 6

Device Drivers:

Answer 6

Program that enables hardware devices to communicate

with the computer’s OS. Part of the OS

Question 7

Buffering/prefetch:

Answer 7

When device op reads more data than user requested (use all n data registers)

Question 8

Interrupt Request Flag (IR Flag)

Answer 8

Requires additional hardware (so requires more complex HW/SW but offers more efficient use of computer resources)

Question 9

“Block-oriented” devices

Answer 9

Transfer a lot of data with 1 I/O request.

Question 10

User mode:

Answer 10

Execution in user role (limited, no privileged instructions)

Question 11

Kernel mode:

Answer 11

Execution is OS role (Privileged instructions allowed)

Question 12

Direct Memory Access(DMA)

Answer 12

Removes CPU from data transfer altogether

1. Smart controller transfers all data directly to memory
2. CPU initiates as before, but adding a memory location to request where result will be stored
3. One interrupt only after all data transferred