Topic 2 - Computer architecture Flashcards
Control Unit
Control the retrieval of instructions from the primary memory as well as the sequence of their execution
Registers
- MAR, MDR
Arithmetic Logic Unit
Performs all basic arithmetic, logical or input/output operations
Memory Address Register
Holds the memory address of the data to be used by the ALU,
so that the ALU can fetch the corresponding content from the memory and process it
It also holds the memory address of data that has been processed and will be stored
Memory Data Register
Holds data that is to be used by the ALU and then saved to the RAM
ALU places the result onto the MDR and the data is copied to the memory address location in the RAM
Data Bus
RAM to MDR
Control Bus
RAM to CU
Memory (address) Bus
RAM to MAR
Machine cycle
- Address of the next instruction stored in MAR
- Data is fetched from main memory and stored in MDR
- CU decodes instruction
- ALU executes command/operation
- Output value stored in accumulator if needed
- processed data stored back on main memory. Address sent along Address Bus, data sent along data bus
Random Access Memory (RAM)
Stores data and instructions of program currently being run.
Data is constantly moved and overwritten.
- Volatile
- All data are deleted once there’s no power
Read Only Memory (ROM)
Stores permanent instructions and data of programs used to boot and operate the computer
- Non-volatile
-Data and instructions remain even when there’s no power
- Smaller than RAM
Cache memory
Type of memory that is smaller and accessed faster than RAM since closer to the CPU.
- Stores most frequently used data and instructions
- Performance speeds up
- Computer checks if there is a copy of data in cache before accessing main memory
Secondary memory
Relatively slow but higher capacity than primary memory
- Can be written to but non-volatile
- Also known as persistent storage
- Contents are not wiped out after process is finished or when there’s no power
Primary memory
The only storage that is directly accessible by the CPU
Startup Memory
- RAM is empty when the computer starts up
- Instructions and data need to be copied into the RAM in order for the computer to run
- Mostly copied from the secondary memory
- Only ROM would be able to store programs and instructions
- ROM cannot be over-written
- Computer would only be able to perform fixed operations
Virtual Memory
Memory management capability of an OS that uses hardware and software to allow a computer to compensate for physical memory shortages by temporarily transferring data from RAM to disk storage
