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CPU
Flashcards on the CPU
34
Computer Science
Not Applicable
09/30/2013

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Cards

Term
What is the purpose of a CPU?
Definition
To process data.
Term
What happens in the CPU?
Definition

The processing of data.


The searching, sorting, calculating and decision making of the computer.

Term
What is the Fetch - Decode - Execute cycle?
Definition
The steps needed for processing to take place.
Term
What happens at the first (FETCH) step of the Fetch-Execute Cycle?
Definition
The CPU fetches data and instructions from main memory to store in its temporary memory areas (registers).
Term
What is the 'address bus?'
Definition
A hardware path that leads from the CPU to the main memory.
Term
What is put on the adress bus by the CPU?
Definition
The address of the next item to be fetched.
Term
What hardware path does the data take from the main memory to the CPU?
Definition
The 'data bus.'
Term
What happens in the second part of the Fetch-Execute cycle with the CPU's 'instruction set'?
Definition
The CPU decodes the data using its instruction set and prepares the chip in readiness for the execute step.
Term
What happens at the third part of the Fetch-Execute cycle?
Definition
The instruction called for is carried out upon the data.
Term
What happens with the result of data processed by the CPU?
Definition
It is stored in another register.
Term
What happens one the execute stage of the Fetch-Execute cycle is complete?
Definition
The CPU sets up to begin the cycle again.
Term
What are the three main parts of the CPU?
Definition
  • Control Unit
  • Immediate Access Store (IAS)
  • Arithmetic and Logic Unit (ALU)
Term
What are the three jobs of the Control Unit?
Definition
  1. Controls and monitors the hardware attached to the system to make sure the commands given by the application software are used correctly.
  2. Controls the input and output of data so the signals go to the right place at the right time.
  3. Controls the flow of data within the CPU.
Term
What does the Immediate Access Store (IAS) do?
Definition
It holds the data and programs needed by the Control Unit at that instant.
Term
Why is the IAS needed?
Definition
Because the Backing Storage (ie the hard disk) is too slow to be able to run applications directly.
Term
What is the Arithmetic Logic Unit (ALU?)
Definition
The part of the CPU that processed data by minipulating it or acting upon it.
Term
What are the two parts of the ALU?
Definition
The Arithmetic part and the Logic part.
Term
What does the Arithmetic part of the ALU do?
Definition

Performs calculations on the data.


ie 2+3=5

 

Term
What does the Logic part of the ALU do?
Definition

The logic and comparisons.


ie = < >

 

Term
What is the clock speed?
Definition
The amount of data a CPU can process in a certain time.
Term
What is the clock speed controlled by?
Definition
A quartz crystal inside the CPU.
Term
What is the clock speed measured in?
Definition
Cycles per second.
Term
What is one cycle per second equal to?
Definition
One Hertz.
Term
How many instructions are being carried out by a computer running at 1GHz?
Definition
A thousand million per second.
Term
What is the typical clock speed of a modern desktop?
Definition
Three thousand million cycles per second (3 GHz).
Term
What does the clock speed affect?
Definition

The performance of the CPU


Higher clock speed = higher performance

Term
What is 'overclocking?'
Definition

The clock is adjusted so it will run faster than originally intended.


This makes the CPU run hotter and so extra cooling fans are needed.

Term
How many processes can a CPU perform at once?
Definition
One.
Term
What do 'dual core' and 'quad core' mean?
Definition

The computer runs with two CPUs or four CPUs.


This makes it perform better (but not exactly twice as well)

 

Term
Where is most data stored?
Definition
The hard disk.
Term
Why is data loaded into the RAM rather than being taken straight from the hard disk?
Definition
Accessing data from the RAM is a lot faster than accessing it from the hard disk.
Term
Why is data stored in the cache memory?
Definition
To avoid delays in getting data to the CPU.
Term
What kind of memory is looked into first for new data and instructions?
Definition
The cache, then the RAM, then the hard disk.
Term
Why is the cache called 'volatile memory?'
Definition
Because when the computer is turned off, the data stored there is lost.
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