4.7.3.1 Fo CompOrgArch (The processor and its components)

Question 1

What is the difference between memory locations and memory addresses

Answer 1

Address - The unique identifier of where the data is stored
Location - The physical location of where it data is stored

Question 2

What is the Program Counter and what does it do

Answer 2

• A special purpose register that stores the address of the next instruction to be executed by the CPU
  -At the start of the FDE its contents are copied onto the MAR
• Before the end of the fetch stage it is incremented

Question 3

What is the MAR and what does it do

Answer 3

-Holds the address of the memory location from which data is to be written, and sends this address to memory via the address bus

Question 4

What is the MDR and what does it do

Answer 4

Used to store data and instructions passed from the RAM to the CPU, and passes it to the appropriate unit ( ALU or CU), and stores data and instructions that is to be passed from the CPU to the RAM

Question 5

What does the ALU do

Answer 5

Performs arithmetic and logic operations and bitwise shift, to execute instructions, and uses general purpose registers to temporarily hold the result of a calculation. It also updates the status register as appropriate following its operation

Question 6

What is the Status register and what does it do

Answer 6

• it holds lots of different values that indicate the result of the last operation executed by the ALU, and so acts as a flag to the state of the CPU

Question 7

What sort of things do the bits in the status register indicate

Answer 7

• Interrupts
• Results (Greater or Less than)
• Overflow and Underflows
• the presence of a carry bit

Question 8

What are general purpose registers and what are they used for

Answer 8

Tiny areas of extremely fast memory located in the CPU, designed to store temporary data while instructions are being carried out
It makes the CPU faster as it doesn’t have to read/write from/to the RAM which is outside of the CPU

Question 9

What is the Control unit

Answer 9

The component within the CPU responsible for directing the operations of the various other component, including determining when tasks should be performed and how they should be executed.

Question 10

What are some notable functions of the Control unit

Answer 10

• Decodes the instruction on the FDE cycle
• Uses the clock to synchronise the components of the CPU

Question 11

What is the Clock

Answer 11

An electronic unit that synchronises related components by generating pulses at a constant rate

Question 12

True/False one instruction takes one clock cycle

Answer 12

• False