Structure And Function Of Processor Flashcards
What does the ALU do?
Performs calculations by receiving Opcodes and Operands. Executes instruction on opcode and outputs result to storage register
What components make up a modern processor?
CU, ALU and Registers
What are the types of registers?
- MAR
- MDR
- PC
- ACC
- CIR
What does the program counter do?
- Contains address of the next instruction to be executed
- Increments when one instruction is read
What does the Accumulator Do?
- Stores result of executions temporarily before being transferred to the memory?
- Hold INP/out data currently being processed
What is the purpose of the Memory Address register?
- Stores address of memory location currently in use
- Allows communication with address bus
- Output goes to address bus
What is they purpose of the MDR?
- Stores data/instructions fetched from memory before use by processor
- Buffer between CPU and memory unit. Makes it so data is written in one big go to the memory instead of writing the data individually. It makes it faster as you are only doing the slow write operation once rather than multiple times
- Allows CPU to communicate with data bus
What is the purpose of CIR?
Stores current instruction to be executed
What are the types of buses and what do they do?
- Control bus = Used to communicate with other devices and components, carrying commands rom CPU + returning status signals
- Data bus = carries information
- Address bus = Carries memory address of data
What does the CU do?
- Sends signals around the processor
- determines how data is transferred between memory-CPU and between components of CPU.
- Decodes instructions
- clock is located in the CU
What is cache Memory?
Small amount of RAM built into CPU. Stores info the CPU is most likely to need next. Faster than accessing RAM. Up to three levels (L1-L3 with L1 being smallest but fastest)
What is the clock rate?
- Determines how fast instructions are executed
- Each ‘tick’ begins when clock switches from 0 to 1
- Ticks are directly proportional to speed
- Measured in MHz or GHz
What happens up in the fetch stage of the cycle?
-PC holds address of next instruction
-This address is copied to the MAR
-The contents of the address in the MAR are copied to the MDR
-contents of MDR copied to CIR
-PC is Incremented and process repeats
LOOK IN PHOTOS FOR DIAGRAM
What happens in the decode part of the cycle?
- CU works out what instruction does
- Checks against a set of instructions held in ROM
- Each instruction had microcode
- Microcode provides a step by step guide on how to perform instruction
- Checks all necessary data is present
- Pass instruction and data to schedule
What happens in the schedule part of the cycle?
- Decides which execute unit to send instruction to
- Depends what type of instruction as to what one it’s passed to
- Passes to execution
