Hardware Flashcards
What is the CPU?
The central processing unit
Name the four main components in the CPU.
The Arithmetic and Logic Unit
The Control Unit
The Registers
The Immediate Access Store
What does the ALU do?
- Performs all arithmetic processes
- Performs all logical process
- Acts as a gateway to the CPU
What does the control unit do?
It is the part the runs the fetch-decode-execute cycle.
What are registers?
They are a type of memory that can be accessed very quickly compared to other types of memory.
What do registers do?
They can be used to store data and control information during a fetch-decode-execute cycle or they can be used to hold values that are generated as part of the ALU working on data.
What is the Immediate Access Store?
The IAS is the place where programs and the data that is needed by programs are held, ready to be fetched then decoded and executed by the CPU. The CPU may also use this place to store the results of any processing it does. It can be thought of as made up of lots of individual ‘memory’ locations, each capable of storing a byte of data.
What affects to performance of the CPU?
- The materials the processor is made from
- The clock speed
- The size of data and address buses
- The word size
What meant by clock speed?
How fast the fetch-decode-execute cycles the CPU can be executed.
eg. 800Mhz means 800 million per second
What is meant by word size?
This is the number of bits that the CPU can work with in any one clock cycle. The more bits it can work with in one clock cycle, the faster the computer will go.
What is the program counter register (PC)?
this holds the address of the next instruction to be fetched and executd
What is the Current Instruction Register (CIR)?
this holds the current instruction being executed
What is the memory address register (MAR)?
this holds the RAM address you want to read to or write from
What is the memory data register (MDR)?
this holds the data you have read from RAM or want to write to RAM
What are the accumulators?
these hold the data being worked on and the results of arithmetic and logical operations
What is the status register?
this holds information about the last operation e.g. whether the least sum done produced a negative result
What is the interrupt register?
this holds details about whether an interrupt has happened
What is the address bus?
This bus, in black on the diagram, is usually a set of wires that links the CPU to the RAM (and to other places). If the CPU want to fetch an instruction from a particular address in RAM, or wants to write a piece of data to a particular address in RAM, it puts the address on the address bus
What is the data bus?
The dotted channels you can see in the diagram is the data bus. The CPU puts data it wants to transfer to RAM on this bus. If data is being fetched from RAM, then it is put on this bus as well.
What is the control bus?
Signals need to be sent around the computer to control when things happen. These signals are sent along the control bus. Tthe striped channel you can see in the diagram is the control bus.