Structure of processor and its functions

Question 1

What are the 3 buses used within a PC?

Answer 1

1. Control bus
2. Data bus
3. Address bus

Question 2

What is used in order to process an instruction?

Answer 2

1. Opcode

2. Operand

Question 3

What is the Control Unit?

Answer 3

A control unit coordinates all of the activities of CPU. Shows flow of data between CPU and other components.
Accepts instruction, decodes it, handles execution, stores resulting data back in memory or registers.

Question 4

What is the ALU?

Answer 4

The arithmetic logic unit (ALU) performs arithmetic or logic operations. Bitwise shifts, Boolean logic gates.
Often use general-purpose registers to temporarily hold results of calculations

Question 5

What is the ACC?

Answer 5

The accumulator (ACC) stores data and control information. The more general-purpose registers a processor has,
the faster it may operate. Results of calculations from ALU are stored here.

Question 6

What is the MAR?

Answer 6

The memory address register (MAR) holds the address of the memory location of data yet to be fetched.
Sends these addresses to memory through the address bus.

Question 7

What is the MDR?

Answer 7

The memory data register (MDR) temporarily stores data which is written to memory or read from memory.
All data to/from memory must travel down the data buss and pass through MDR.

Question 8

What is the CIR?

Answer 8

Current instruction register (CIR) = Holds current instruction that’s being executed. Contents of MDR copied to CIR
if instructed to. Has opcode and operand.

Question 9

What is the PC in a processor?

Answer 9

The program counter (PC) holds address of next instruction yet to be executed.

Question 10

What is the DU?

Answer 10

The decode unit (DU) is a piece of logic that is presented with a sequence of bits that have been fetched from memory.
Prepares execution of instruction by looking up the binary operation code in its table so CPU knows what to do.

Question 11

What do each of the busses do?

Answer 11

1. Control bus = carries commands and control signals to and from every component of CPU
2. Data bus = carries 1s and 0s that make up actual info being transmitted around CPU from RAM to CPU.
3. Address bus = carries memory addresses that tell where data is read from/written to.