Structure and Role of the Processor and its Components Flashcards
What do processors contain
ALU (Arithmetic Logic Unit)
Control Unit
PC
CIR
MAR
MBR
SR
What is the role of the ALU
To perform arithmetic and logic operations
What is the control unit responsible for
Controls the hardware, including I/O and CPU
Controlling the fetch execute cycle
What are registers
Small storage locations used to hold data temporarily
What are General Purpose Registers
Registers that can be manipulated to perform the role of any other registers
List the Special Purpose Registers
Program Counter (PC)
Current Instruction Register (CIR)
Memory Address Register (MAR)
Memory Buffer Register (MBR)
Status Register (SR)
What does a Program Counter do
Hold the memory address of the next instruction to be executed in the fetch-execute cycle
What does the Current Instruction Register do
Holds the instruction that is currently being decoded and executed by the processor
What does the Memory Address Register do
Stores the memory address of an instruction that is to be read from, or the address in memory to which data is to be transferred
What is the role of the Memory Buffer Register
Holds the content of a memory location that has been read from or data that is stored to
Place where all communications between the CPU and Memory take place
What is the role of the Status Register
Contains a number of bits, the values of which can change to indicate the occurrence of an interrupt
What is the clock
A device that generates a timing signal which changes at a regular frequency which regulates all of the actions that take place
When is the signal generated by the clock used
To synchronise communication between the components of the processor and the rest of the computer system
What happens during the fetch stage of the fetch execute cycle
Content of the PC is copied to the MAR
Content of the MAR is transferred to the main memory by the address bus
Instruction is sent from main memory to the MBR by the data bus
PC is incremented by one
Content of the MBR is copied to the CIR
What happens during the decode stage of the fetch execute cycle
Content of the CIR is decoded by the control unit
Decoded instruction is split into two parts - opcode and operands
What happens during the execute stage of the fetch-execute cycle
Any data required by the instruction that isn’t present is fetched
The instruction is carried out
Results of any calculations are stored in general purpose registers or main memory
What are instructions usually stored in and how
Machine code
Two primary parts - opcode and one or more operands
What does the opcode specify
Type of operation that is to be carried out
What is the operand
Pieces of data on which the operation is performed
What are the two types of addressing modes
Immediate and direct
What happens in immediate addressing
The value specified in the operand is to be treated as the actual value
What happens in direct addressing
Value specified by an operand signifies a memory address
What is an interrupt
A signal sent to the processor by another part of the computer requesting the attention of the processor
What happens when an interrupt occurs
It is detected as a change in the content of the status register between the execute and fetch stages of the fetch-execute cycle
What are the two approaches used in instruction sets
RISC (Reduced Instruction Set Computer)
CISC (Complex Instruction Set Computer)
RISC vs CISC
RISC executes one instruction per clock cycle
CISC - each instruction performs so many actions that it takes several clock cycles to complete
What Factors affect Processor Performance
Amount of Cores
Cache Memory
Words
Clock Speed
Bus Width
