1.1 Systems Architecture

Question 1

What is a CPU, and what does it do?

Answer 1

The Central Processing Unit. It carries out all the commands and processes information.

Question 2

What is clock speed?

Answer 2

The clock speed is how many FDE (Fetch Decode Execute) cycles the CPU can do in a second. It is measured in Hz (Hertz)

Question 3

what are some of the characteristics of cache

Answer 3

• faster than RAM
• Stores commonly used instructions
• Volatile and small
• Really expensive

Question 4

what is the PC and what does it do?

Answer 4

Program counter
Stores the address of the next instruction to be run, it increments by one each time

Question 5

How does the number of cores affect CPU speed?

Answer 5

The cores act as another CPU.
The more cores means more instructions can be carried out.
However it is only useful when the applications are programmed to handle it.

Question 6

What is the ACC and what does it do?

Answer 6

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

Question 7

What is the MAR and what does it do?

Answer 7

Memory Address Register.

Contents of the PC are copied here.
Stores the address where the next data will be fetched from

Question 8

What is the MDR and what does it do?

Answer 8

Memory Data Register.
Stores data / instructions being brought back from the RAM.

Question 9

What is the CIR and what does it do?

Answer 9

Current Instruction Register.
The instructions / data in the MDR are copied here.

Question 10

Data Bus

Answer 10

Carries data around (can go both ways)

Question 11

Address Bus

Answer 11

Carries around addresses (can only go one way)

Question 12

Control bus

Answer 12

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

Question 13

What is the ALU and what does it do?

Answer 13

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

Question 14

What is the CU and what does it do?

Answer 14

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

Question 15

What is Von Neumann Architecture?

Answer 15

Data + instructions are stored in the same RAM location. The FDE cycle is then used to decode and execute instructions.

Question 16

What is an embedded system?

Answer 16

A computer system inside a larger computer system

Question 17

In the FDE cycle what takes place in the ‘Fetch’ sector?

Answer 17

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

2) Copy instruction stored in MAR –> MDR.

Question 18

In the FDE cycle what takes place in the ‘Decode’ sector?

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

In the FDE cycle what takes place in the ‘Execute’ sector?

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.