1.1.1 - Structure and Function of the Processor Flashcards
What is the CIR and what is its purpose?
- Current Instruction Register (CIR) - Holds the instruction while it is being decoded/executed.
- Contents are split into opcode and operand
- operand is copied to MAR if it is an address or MDR if it is data
What is the MDR and what is its purpose?
Memory Data Register (MDR) - Contains the instruction or data which has been accessed from memory
What is the MAR and what is its purpose?
Memory Address Register (MAR) - Contents of the PC are copied here in order for the processor to access the next instruction
What is the ACC and what is its purpose?
Accumulator (ACC) - Temporary storage for data being processed (input and output) - Holds results of calculations (from the ALU)
What is the PC and what is its purpose?
Program Counter (PC) - Stores the address of the next instruction to be fetched
What is the CU and what is its purpose?
Control Unit (CU) – Decodes instructions and sends out control signals
What is the purpose of the address bus?
Address Bus – Carries the address where the data is going to or from
What is the ALU and what is its purpose?
The Arithmetic and Logic Unit (ALU) - Carries out calculations and logical instructions
What is the purpose of the data bus?
Data Bus - Carries the data from one place to another
What is a register?
Register - Small piece of temporary memory located within the processor/CPU. Used for a specific purpose.
What is the purpose of the control bus? What CPU component would use this bus?
Control Bus - Carries control signals from the control unit to other parts of the system
What are the sub-stages of the fetch part of the FDE cycle?
- Data/address is copied from PC to MAR
- PC is incremented (usually by 1)
- Data in MAR is passed onto the Address Bus
- Conrol unit sends read signal onto the control bus
- RAM copies the data from the location specified by the address bus along the data bus
- Data on the data bus is stored in the MDR
- Data is copied from the MDR to the CIR
What are some key facts about the Von Neumann Processor
- Data and Instructions are stored in the same area of memory in the same format
- Uses the same bus for data and instructions - can only fetch either data or instructions at one time
- Design is less complex - development is cheaper
- Single CU / ALU
- Uses the special registers (MDR, ACC etc..)
- Follows the Fetch Decode Execute cycle
What are some key facts about the Harvard Processor
- Separate memory for instructions and data - could fill unequally
- Has separate data and address buses for instructions
- Can read/write data and instructions simultaneously
- Has fixed memory sizes for data and Instructions
- Development is more expensive. More CPU pins are required; a complex motherboard is required with doubling of memory
What is a contemporary architecture and what features may it have?
AKA - Modern Processors - Has aspects of both Von Neumann and Harvard.
Have features such as:
- Pipelining
- Make use of cache
- Virtual Cores
- Hyper Threading
- Multiple Cores
- On-board Graphics
