Internal Computer Architecture

Question 1

System Bus

Answer 1

A communication system that transfers data between components in a computer

Question 2

Data Bus

Answer 2

A bi-directional bus that carries instructions and data between devices

Question 3

Control Bus

Answer 3

A bi-directional bus that carries control signals. Prevents conflict in the system.

Question 4

Address Bus

Answer 4

A uni-directional bus that transfers addresses from the processor to the main memory, in order to place their contents on the data bus

Question 5

ALU

Answer 5

Arithmetic Logic unit - completes arithmetic and logic operations, such as ADD, SUBTRACT, AND or XOR

Question 6

Harvard Architecture

Answer 6

A type of computer organisation where instructions and data are stored in physically different locations.

Question 7

Von Neumann Architecture

Answer 7

Instructions and data are stores in the sane location

Question 8

I/O controller

Answer 8

A device that interfaces between an input/output device and the processor. They receive input and output requests from the processor and send device-specific signals to the device they control.

Question 9

The stages of the Fetch-Execute Cycle:

Answer 9

MAR

Question 10

How is addressable memory calculated?

Answer 10

It depends on the width of the address bus: a 16-bit address bus can address 2^16 values in memory, values 0 to (2^16)-1

Question 11

What factors affect computer performance?

Answer 11

Clock speed, word length, address bus width, data bus width, number of cores, size/type/location of cache

Question 12

Why is the data bus bi-directional?

Answer 12

In order to carry data and instructions between devices and main memory as needed.

Question 13

Name/describe some control signals transmitted by the control bus:

Answer 13

Memory read/write - data from the addressed location is read to the data bus/data from the data bus is written to memory
Interrupt read - a device with lower priority wants to use the CPU
Bus request - indicates that a device wants the use of the data bus
Bus grant - CPU has granted access to the data bus
Clock - synchronise operations
Reset - initialises all components

Question 14

Why is the address bus uni-directional?

Answer 14

Only the processor sends addresses to memory.

Question 15

Why is the control bus important?

Answer 15

It ensures that there are no conflicts in bus usage, as only one device may transmit down a bus at a given time.

Question 16

What happens when an instruction is longer than data bus width?

Answer 16

The processor must access memory twice to fetch the instruction.

Question 17

Describe the stored program concept:

Answer 17

A single store is used to hold data and instructions ( the program). A program must be resident in main memory to be execution - instructions are fetched one at a time, decoded and executed.

Question 18

Which devices can write to the data bus? Which can read from it?

Answer 18

Write: The processor, input controllers, disk I/O controller, main memory
Read: The processor, output controllers, disk I/O controller, main memory