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 Arithmetic Logic Unit (ALU) do?

Answer 9

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

Question 10

What does the Control Unit (CU) do?

Answer 10

Manages the data:
Controls where data goes and monitors the flow of data.
Executes instructions.
Sends control signals between the different internal components.

Question 11

What is Von Neumann architecture?

Answer 11

Data + instructions are stored in the same RAM location.

FDE cycle is then used to FDE the instructions

Question 12

What is an embedded system?

Answer 12

Computer system inside a larger computer system.

Question 13

What happens in Fetch?

Answer 13

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

2) Copy instruction stored in MAR –> MDR.

Question 14

What happens in Decode?

Answer 14

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 15

What happens in Execute?

Answer 15

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.