1.1.1 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
- Read signal is sent onto the control bus
- RAM copies the data from the location specified by the address bus onto the data bus
- Data on the data bus is passed into 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
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
- Has separate data and address buses for instructions
- Instructions and data can be retrieved in parallel
- Has fixed memory sizes for data and Instructions
- Instruction memory may be ROM
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
