Computer Hardware Flashcards
In the fetch- decode-execute cycle, define the term:
Fetch
The CPU retrieves an instruction from the main memory.
In the fetch- decode-execute cycle, define the term:
decode
Working out what needs to be done to carry out the instruction.
In the fetch- decode-execute cycle, define the term:
Execute
Carrying out what is specified by the instruction.
What does the following stand for:
CPU
Central Processing Unit
What does the following stand for and what does it do:
CU
Control Unit
* Manages how data is processed by the CPU
* Manages how CPU and other components communicate
* Executes all instructions
* Informs other devices how to respond to instructions
In summary the main job of the CU is to:
- To decide which instruction to carry out next and fetch it from memory.
- To decode the instruction (work out what needs to be done to carry the instruction out).
- To execute the instruction.
What does the following stand for and what does it do:
ALU
Arithmetic and logic unit
* Processes data that requires arithmetic caulculations e.g. add
* Performs logical comparisons e.g. And, Or
* Usually has a register (accumulator) to store intermediate results
What does the following stand for and what does it do:
IAS
Immediate Access Store
* Also known as main memory
* Stores all programs & data temporarily while in use
* Often referred to as registers (very small amount of storage)
* In a 64-bit processor each register will store 64 bits.
* During Fetch-Execute cycle instructions are fetched from specific storage location in the IAS using an address
* Each memory location has a unique address
How many registers do we have to help process data in the FDE cycle?
5
What are the 5 registers used in the FDE cycle?
- Program counter (PC)
- Memory address register (MAR)
- Memory data register (MDR)
- Instruction register (IR)
- Accumulator
What does computer hardware include?
The physical parts of a computer system.
- Input devices
- Processing devices
- Storage devices
- Output devices
Give examples of
Input devices
Keyboard
Mouse
Microphone
Give examples of
Output devices
- Monitors
- Speakers
- Printers
Give the definition of an
Input device
A device that allows us to put raw data into a computer.
Give the definition of an
Output device
Devices that let the computer communicate with the user.
What are the two types of storage?
A main store - ROM/RAM
Backing Store - can be internal (hard disk) or external (USB dirve)
What are the 3 categories internal memory can be divided into
- RAM - Random Access Memory
- ROM - Read Only Memory
- Cache
Describe RAM
Memory that can be read from or written to
Volatile - will be lost when computer is switched off
Holds data/programs that are currently being used
Describe ROM
Can be read from but not written to
Data stored is permanent - can’t be changed
Non-volatile - used to store programs frequently used by the computer
Describe cache
RAM is compartively slow compared to speed of registers
Cache is used to store data that is frequently used, recently used or about to be used
Means that data doesn’t have to be fetched from RAM
How many tasks does the CPU complete at one time?
One.
What is an instruction?
An action that a program wants the CPU to carry out.
What are the two parts of an instruction?
Operator - what operation needs to be done
Operands - the data
What does the Program Counter do?
- Stores the address of the next instruction
- As many program instructions are stored in sequence the program counter is automatically increased by 1 each time an instruction is fetched
- The program counter stores the next instruction address in the sequence
What does the Memory Address Register do?
- All program instructions are stored in the main memory of the CPU in a number of memory locations.
- Each memory location contains a unique address.
- The address of the current instruction or data being executed is temporarily stored in the MAR.
What does the memory data register do?
- Temporarily stores data fetched from or written to the main memory of the CPU
- All data transferred from main memory to CPU goes via MDR
What does the instruction register do?
Temporarily stores the current instruction to be decoded and then executed
What does the accumulator to?
- Dedicated register that is part of the ALU
- When calculating results are initially stored in the accumulator before being stored in the main memory
- Default location to store any calculations performed by the ALU
Give 2 factors that can influence the speed of processing
Processor clock speed
Cache
