Processor Hardware and Instruction Sets

Question 1

What is the instruction cycle?

Answer 1

Fetch instruction from memory
Decode instruction
Fetch operands
Perform computation
Write result to memory

Question 2

What is pipelining?

Answer 2

Pipelining speeds up processing by starting an instruction before the previous one is complete. This only works if each instruction is one word long at each stage.

Question 3

Describe CISC

Answer 3

Instructions can be any length
Instructions can be any format
Instructions can take any number of clock cycles
Difficult for pipelines to handle

Question 4

Describe RISC

Answer 4

Instructions are one word long
Instructions are all a similar format
Instructions take one clock cycle to execute

Question 5

What are the key registers in a CPU?

Answer 5

PC - holds the address of the next instruction
MAR - holds the address issued to the address bus
MDR - exchanges data with the data bus
IR - holds the current instruction
SP - hold current address at the top of the stack
SR - holds the status bit

Question 6

What are the four status flags?

Answer 6

C - calculation produced a carry bit
V - calculation produced a signed overflow
Z - result is zero
N - result is negative

Question 7

What is a machine instruction?

Answer 7

A binary word that encodes the operation to be carried out, the location of the operands and the location to store the result.