Components Of A Computer Flashcards
What does the control unit do?
Controls and coordinates what the CPU is doing. Directs the flow of data between CPU and other devices. It accepts the next instruction, decodes it into several steps and manages its execution.
What is a bus?
A bus is a set of parallel wires connecting two or more components of a computer.
What are the three buses the CPU is connected to?
address, data and control
How does the CPU use the address bus?
When the CPU wants to access a location in the main memory, it sends the address to the memory along the address bus.
How is the data bus used?
Data retrieved from the main memory is returned to the CPU on the data bus
What is the ALU?
Arithmetic Logic Unit. Performs arithmetic and logical operations.
Name the five registers in the CPU
Program Counter Current Instruction Register Memory Address Register Memory Data Register Accumulator
Not the ALU idiot
What is the PC used for?
Holds the address of the next instruction to be executed.
What is the CIR used for?
Holds the current instruction being executed, divided into operand and opcode
What is the MAR used for?
Holds the address of the memory location where data is being retrieved/written to
What is the MDR used for?
Used to temporarily store the data read from or being written to memory.
Describe the fetch phase of the Fetch-execute cycle
The address of the next instruction is copied from the PC to the MAR.
The contents of the MAR are sent along the address bus to main memory.
The data held at that address in memory is returned along the data bus and copied to the MDR. Simultaneously the content of the PC is incremented.
The contents of the MDR are copied to the CIR.
Describe the decode phase of the fetch-execute cycle
The instruction in the CIR is passed to the decode unit to be decoded by splitting it into the opcode and operand.
The decoded address is stored in the MAR.
It goes along the address bus to the address in the main memory. The data there is passed along the data bus and stored in the MDR and is then sent to the ALU where it is executed.
What is the accumulator used for?
Used to save the result of operations carried out in the ALU.
What is pipelining?
As the current instruction is being executed in the ALU, the next instruction is being fetched from memory.
What is von Neumann architecture?
Data and instructions are together in memory. The same data bus is used to transfer both data and instructions from main memory and a single address bus is used.
What is the stored program concept?
machine code instructions are fetched and executed serially by a processor that performs arithmetic and logical operations.
What is Harvard architecture?
When instructions and data are stored in two different memories. This allows for parallel data and instruction buses to be used.
What is CISC?
Complex Instruction Set Computers. Complex instructions are built into the machine’s hardware, which means less lines of code have to be written in the assembly program.
What is RISC?
Reduced Instruction Set Computer. Only simple instructions that take one clock cycle are available.
What are the advantages of CISC? (3 things)
The compiler has to do less work to translate high level languages into machine code.
The instructions are short, so they take up less space in RAM.
Programmers writing in assembly have to write less code
What are the disadvantages of CISC?(3 things)
Many specialised instructions are built into the hardware that are rarely used.
Processors require more circuitry and so are more expensive to make
Processors use more power as they contain more components such as capacitors.
What are the disadvantages of RISC? (3 things)
The compiler has to do more work to translate high level languages into machine code.
The instructions are large, so they take up more space in RAM.
Programmers writing in assembly have to write more code.
What are the advantages of RISC?(2 things)
All instructions take the same time, so pipelining is possible.
Processors have less circuitry so they are cheaper to make.
What is a co-processor?
An extra processor used to supplement the functions of the primary processor. It may be specialised at performing a certain task, such as handling graphics.
What are the advantages of a multi-core system?
Allows you to process one set of instructions faster by splitting the workload between different cores.
Allows you to run multiple programs at one time.
What does a GPU do?
A GPU handles computer graphics and image rendering. It is very efficient at doing repetitive tasks, such as updating the pixels on a monitor.
What is the structure of a GPU?
A GPU is made up of thousands of small cores connected in a parallel architecture.
Name 4 factors that affect the performance of a CPU
Clock speed
Number of cores
Cache memory size
If pipelining is being used
What is contemporary architecture?
Contemporary processors use a combination of Harvard and Von Neumann architecture.
Von Neumann is used when working with data and instructions in main memory, but uses Harvard architecture for the cache.
