1.2 - The Fetch Execute Cycle Flashcards
Where is the computer’s memory?
The computer’s memory is very close to the CPU.
How is the CPU and Memory joined?
By buses
When people refer to the CPU and Memory , what do they call it?
Processor
What are three memory types?
Secondary storage: is used to save user data files and program files in a non-electrical form until they are needed by the processor.
Immediate Access Store (IAS): Computer’s ability to go directly to a requested file or piece of data instead of sifting through a list
Random Access Memory (RAM): primary storage that holds data ready to be used by the CPU.
What does memory hold?
-The instructions that tell the computer what to do.
-The data values that the computer needs
-The results of the CPU’s work.
How do modern computers transfer data and instructions differently?
In a modern computer the instructions and data are held in the same memory. But they go down two different buses to the CPU.
When the CPU completes an instruction, what does it do with the results?
It sends the results back to memory
What is memory made up of ?
-Memory is made of microscopic electrical circuits.
How does memory work?
The memory circuits can be on or off. Everything inside the memory is stored using these on / off signals.
How is data stored in memory?
How is data lost in memory ?
Data is stored in memory as electrical signals. But if the electricity is turned off, all the data will be lost.
What happens when you save your work?
Data is copied from memory to storage
What are some examples of storage ?
-The hard disk of your computer
-A flash memory drive
-The storage on your school network
-Cloud storage on the internet
What is another name of storage ?
Secondary storage
What is secondary storage?
Peripherals such as storage drives. Secondary storage is used to save user data files and program files in a non-electrical form until they are needed by the processor.
What are the advantages of RAM (electronic memory)?
RAM is very close to the CPU. The CPU can get data and instructions form RAM easily and quickly.
What are the disadvantages of RAM (electronic memory)?
The disadvantage of RAM is that it’s contents are lost when the computer is switched off.
What are the advantages of the secondary storage ?
The secondary storage can keep data and instructions safe when they are not needed, or when the computer is turned off.
What are the disadvantages of secondary storage?
Secondary storage is further away from the CPU. It takes longer for the CPU to get data and instructions from the secondary storage than from RAM.
What is the fetch-execute cycle?
The actions that take place in a CPU during a single processing cycle.
What are the fetch-execute cycle steps?
1) Fetch
2)Decode
3)Execute
4)Save
Describe the Fetch step:
The control unit ‘fetches’ the instruction from RAM. The instruction travels down the bus from RAM to the control unit.
Describe the Decode step:
The instruction is in the form of a binary code. The control unit knows all the binary number codes. The control unit ‘decodes’ the instruction, so it knows what to do.
Describe the Execute step:
The control unit sends a signal to the ALU to tell it what to do. The ALU carries out the instruction. ‘Execute’ means carry out an instruction.
Describe the Save step:
If the instruction produces a result, then the ALU sends the result back to RAM.
In what form does the instruction arrive to the control unit?
In binary numbers
Which part of the CPU know binary codes?
Control unit
What 2 things affect the speed of the computer?
-The speed of the clock
-The size of the memory
What happens if a computer has lots of RAM?
If a computer has lots of RAM,
then all the data and instructions can fit into the memory.
The CPU can get the data and instructions very quickly .
The computer will go quickly.
What happens if a computer doesn’t have very much memory?
If a computer doesn’t have very much memory,
then the data and instructions won’t all fit into the memory.
Some will have to wait in storage .
The CPU will get the data and instructions slowly.
The computer will go more slowly.
What is cache ?
A small area of primary storage that holds data and instructions that are about to be processed by the CPU.
How close is the cache to the CPU?
The CPU has a small amount of memory (cache) which is even closer than RAM.
What happens if a computer has a big cache?
It is very quick for the CPU to get data and instructions from cache.
If a computer has a big cache then it will be able to get all the dat and instructions quickly.
What is word size?
The amount of data that a computer can fetch and use in one cycle is called the ‘word size’.
How is the size of the buses in different word sizes?
Computers with a larger word size tend to have larger buses so they can carry more data in one cycle.
How does word size affect a computer’s speed?
A computer with a larger word size generally works more quickly
