1.1.1 Structure and function of processor Flashcards
ALU
The arithmetic logic unit carries out the arithmetic and logic operations
The control unit
it is a processor which coordinates the operations of the cpu, this includes managing the flow of data between the cpu and other devices, decoding instructions etc
what are registers
registers are small memory cells that operate at a very high speed. They are used to temporarily store data and all arithmetic, logical and shift operations occur in these registers.
program counter (pc)
holds the address of the next instructions to be executed.
Accumulator ( ACC )
stores the results from calculations
Memory address register ( MAR )
holds the address of the location that is to be read from or written to
memory data register (MDR)
temporarily stores data that has been read from or data that needs to be written
Current instruction register ( CIR )
Holds the current instruction being executed, divided up into operand and opcode
Data bus
This is a bi-directional bus used for transporting data and instructions between components
Address bus
transmits memory address of data to be sent to or retrieved from. The width of the address bus is proportional to the number of addressable memory locations
Control bus
a bi-directional bus used to transmit control signals between internal and external components
Assembly code
this is a simplified way of representing machine code, it uses mnemonics to represent instructions, for example ADD represents addition
operand
this contains the data or the address of the data which the operation is to be performed on
opcode
this specifies the type of instruction to be executed
The fetch-Decode-Execute cycle
The fetch-decode-execute cycle is the sequence of operations that are completed in order to executed an instruction
Fetch
- address from the pc is copied to the MAR
- Instructions held at that address is copied to MDR via the data bus
- At the same time, the contents of the PC are increased by 1
- The value held in the MDR is copied to the CIR
Decode
- The contents of the CIR are slit into operand and opcode
- It is the Decoded by the control unit
Execute
- The decoded instruction is then carried out
Factors affecting CPU performance
- Clock speed
- Number of cores
- Cache size and type
How does clock speed affect CPU performance
The higher the clock speed the more instructions that can be executed per second
how does the number of cores affect cpu performance
A computer with multiple cores can complete more than one FDE cycle at at any given time. a dual core processor could complete tasks twice as fast as a single core one. However, not all programs are able to utilise multiple cores efficiently
how does cache size affect CPU performance
more information can be stored on the CPU’s onboard memory therefore more instructions can be accessed quicker
Level 1 cache
-Very fast memory cells with a small capacity. (2-64KB)
Level 2 Cache
Relatively fast memory cell, with medium sized capacity. (256KB-2MB)
