1.1 Systems Architecture

Question 1

What is a CPU?

Answer 1

Central Processing Unit made of silicon and has billion of switches inside.
Carries out all the commands and processes information.

Question 2

What is clock speed?

Answer 2

Measured in Hz and corresponds with how many FDE cycles the CPU can do in a second:
4GHz= 4 billion FDE cycles per second.

Question 3

What is cache?

Answer 3

Storage location faster than RAM.
Stores commonly used instructions (don’t have to go to CPU to FDE).
Volatile and small.
Really expensive.

Question 4

How does the number of cores affect CPU speed?

Answer 4

Cores act as another CPU:
More cores = more instructions carried out.
Only useful when the applications are programmed to handle it.

Question 5

What does the PC do?

Answer 5

Stores the address of the next instruction to be run

Increments by 1 each time

Question 6

What does the ACC do?

Answer 6

Holds the data (number) that you are currently working on / result from ALU.

Question 7

What does the MAR do?

Answer 7

Contents of the PC are copied here.

Stores the address where the next data will be fetched from

Question 8

What does the MDR do?

Answer 8

Stores data / instructions being brought back from the RAM.

Question 9

What does the CIR do?

Answer 9

The instructions / data in the MDR are copied here.

Question 10

What does the data bus do?

Answer 10

Carries data around (can go both ways).

Question 11

What does the address bus do?

Answer 11

Carries around addresses (can only go one way).

Question 12

What does the control bus do?

Answer 12

Sends signals to the RAM to either re-write or bring the data back.

Question 13

What does the Arithmetic Logic Unit (ALU) do?

Answer 13

Does the arithmetic (mathematical) and logic calculations within the computer.

Question 14

What does the Control Unit (CU) do?

Answer 14

Sends control signals between the different internal components

Controls where data goes and monitors the flow of data.

contains decoder

Executes instructions.

Question 15

What is Von Neumann architecture?

Answer 15

Data + instructions are stored in the same RAM location.

FDE cycle is then used to FDE the instructions

Question 16

What is an embedded system?

Answer 16

a computer system that is part of a larger system

Question 17

What happens in Fetch?

Answer 17

1) Memory address is copied from PC –> MAR.

2) Copy instruction stored in MAR –> MDR.

Question 18

What happens in Decode?

Answer 18

1) Instruction in the MDR is decoded by the CU.

2) CU may then prepare for the next step e.g. loading values into the MAR or MDR.

Question 19

What happens in Execute?

Answer 19

1) Instruction is executed.
2) PC is incremented so the CPU can now execute the next instruction in memory.
3) Before a new instruction is incremented, CPU checks for interrupts.