Unit 1.1 - Systems Architecture

Question 1

Purpose Of The CPU

Answer 1

Continuously perform the
FDE cycle (Fetch, Decode, Execute)
Fetch Data & Instructions form Memory, Decodes and executes instructions

Question 2

CU (Control Unit)

Answer 2

Controls the way data flows around the CPU

Question 3

PC (Program Counter)

Answer 3

Stores the address of the data / instruction to be processed NEXT.

Question 4

MAR (Memory Address Register)

Answer 4

Stores the address

of the data / instruction to be processed (Fetch/read)

Question 5

MDR (Memory Data Register)

Answer 5

Stores the

data / instruction to be processed (fetch/read).

Question 6

ALU (Arithmetic Logic Unit)

Answer 6

Performs Arithmetic Calculations & Logical Operations

Question 7

ACC (Accumulator)

Answer 7

Stores the result of calculations by the ALU

Question 8

IR (Instruction Register)

Answer 8

Stores instruction

currently being Processed

Question 9

Registers

Answer 9

Temporary store of data on the CPU

(While the CPU performs the FDE Cycle it will
shift data in and out of the registers
such as the MAR, MDR, PC, ACC, IR)

Question 10

Purpose of Cache

Answer 10

Stores frequently used
Instructions & Data

More Cache = More instructions & data stored less FDE Cycles used accessing main memory so programs run faster.

Question 11

Clock Speed

Answer 11

The number of FDE cycles
the CPU can perform per second

Faster Clock speed = Faster FDE Cycles so more FDE cycles in a given time.

Question 12

CPU Cores

Answer 12

Multiple CPUs
sharing the workload

More Cores = More FDE cycles can be completed in a given time.

Some tasks /software cannot be split/run across multiple cores.

Question 13

An Embedded System

Answer 13

A computer system that is built into a product that performs a
dedicated function.

Question 14

Embedded Systems - Features

Answer 14

1. Smaller than a PC.
2. No unnecessary features.
3. Usually automated.
4. Software stored in ROM needs firmware update to change.

Question 15

Embedded Systems - Examples

Answer 15

Microwave,
Washing Machine,
Dishwasher,
Watch,
Sat Nav

Question 16

Instruction Set

Answer 16

Set of commands
written in machine language
that the CPU understands

Question 17

Opcode

Answer 17

Part of the instruction that tells the CPU What to do

Question 18

Operand

Answer 18

Part of the instruction that is the Value or Memory location

Where to do it

Question 19

Von Neumann Architecture

Answer 19

Instructions are fetched, decoded and executed one at a time.

Instructions and data are held together in the same memory space.

Question 20

Fetch (FDE Cycle)

Answer 20

The CU sends the contents of the PC to the MAR
The CU then sends READ command on the Control Bus and Address of the data needed on the Address Bus.
The contents of Main Memory are sent via the data bus into the MDR.
The CU copies the data from the MDR to the IR
The PC is incremented so that it points to the next instruction to be executed.

Question 21

Decode (FDE Cycle)

Answer 21

The CU decodes the instruction using an Instruction Set

The instruction is separated into the Opcode & Operand

Question 22

Execute (FDE Cycle)

Answer 22

The function of the instruction is performed.
Move data to and from memory.
If the instruction involves arithmetic or logic, the ALU is utilized.
The ALU may utilize the ACC if it needs to store data to perform the calculation

Question 23

BUS

Answer 23

Allow data to travel between the components, memory & other hardware.

Question 24

Data Bus

Answer 24

Used to send the data / instructions needed from/to memory.

Bi-Directional
(both ways).

Question 25

Control Bus

Answer 25

Used to send write to/read commands to components.

Bi-Directional
both ways - can receive status signals from other components

Question 26

Address Bus

Answer 26

Used to send the Address of the data / instructions needed.

Uni-Directional
one way only from the CPU to Memory