Comp organisation and architecture

Question 1

Role of processor

Answer 1

A device that follows out computation on data by following out instructions

Question 2

Role of main memory

Answer 2

Stores data and instructions that will be used by the processor. It is connected to the processor by several different buses

Question 3

Types of main memory

Answer 3

RAM - Temporary storage space with quick access times
- Volatile (all contents lost when turned off)

ROM - permanent store of data and instructions that can be accessed by the computer
-Not volatile

Question 4

Uses of RAM

Answer 4

Allows programs and software to run
Stores data and instructions needed by processor for FE cycle
Part of OS is loaded in RAM

Question 5

Uses of ROM

Answer 5

Boot program

Question 6

Buses

Answer 6

A set of parallel wires that transmit signals between components, connecting the processor to several I/O controllers

Question 7

Role of address bus

Answer 7

• Uni directional from PROCESSOR–> MEMORY

- Used to access anything stored in main memory so the data bus can access

Question 8

Role of data bus

Answer 8

Carries data and instructions MemoryProcessor

Bi directional

Question 9

Role of control bus

Answer 9

Carries control signals (timing or memory read/write)

Bi directional

Question 10

Role of I/O controllers

Answer 10

• Translates between processor and peripherals
• Buffers data from CPU to device so processor doesn’t have to wait for each device to respond (I/O respond slower to processor)
• Sends specific control signals to the I/O devices from processor
• I/O connected to controllers by ports so can exchange data

Question 11

Von Neumann

Answer 11

Technique used for building a processor where…

Data and instructions are stored in the same memory and accessed via buses

Question 12

Where is von neumann used?

Answer 12

General purpose computers

Question 13

Harvard architecture

Answer 13

Uses separate buses and memory for data and instructions

Question 14

Where is Harvard used?

Answer 14

Embedded devices (mobiles, burglar alarms, DSP)
Digital signal processing - real world continuous data compressed to enable faster processing
Microprocessors
Micro controllers

Question 15

Advantages of Harvard over VN

Answer 15

-Data and instructions can be accessed simultaneously and are handled quicker as don’t have to share same bus
-Reduce delays waiting for memory fetches
-Instructions and data can have different word length
-Avoids possibility of data being executed as code, which is one
method that can be exploited by hackers

Question 16

Addressable memory concept

Answer 16

The concept that data and instructions are stored in memory using discrete addresses

Question 17

Stored program concept

Answer 17

Machine code instructions stored in main memory are fetched and executed serially by a processor that performs arithmetic and logical operations

Question 18

ALU

Answer 18

A component inside the processor which carries out 2 types of operations on data: arithmetic and logic (comparing >

Question 19

Control Unit

Answer 19

Supervises fetch-execute cycle

Makes sure all data is sent to right place (ie right register/section of memory)

Question 20

Clock

Answer 20

Generates electrical pulse (GHZ) to sychronise components of computer eg FE cycle

Question 21

Registers

Answer 21

Small temporary storage in processor

Question 22

Name the dedicated registers in the processor

Answer 22

PC - stores memory location of next data/instruction to be fetched
CIR - Stores instruction currently being executed by processor
MAR - Stores memory location where data in MBR is about to be written to/read from
MBR/MDR - Stores data just been read from/ is about to be written from main memory
SR - Keeps track of status of various parts of comp eg If overflow error occurs

Question 23

Fetch Execute Cycle

Answer 23

PC contains memory location of next instruction to be fetched
Processor transfers this memory location into MAR, then sent down address bus to main memory
Data/instruction in this location sent down data bus back to processor and into MBR. PC is then incremented by 1
Goes into CIR before control unit, where it is decoded and executed by the relevant part of processor (part of ALU)
SR stores any overflow errors if they were to occur

Question 24

Processor instruction set

Answer 24

• Pattern of 0s and 1s a particular processor recognises
• The range of instructions a CPU can execute
• Instruction sets are processor specific

Question 25

LDA #23 which is opcode and which is operand?

Answer 25

LDA # opcode includes basic machine operation and addressing mode
23 is opcode - data/address

Question 26

Direct addressing

Answer 26

Operand is address location of data

Question 27

Immediate addressing

Answer 27

without memory location - operand is the data #