CPU Flashcards
(14 cards)
What does the Control Unit (CU) do?3
•Coordinates all activities and communicates with all parts of the CPU
•Directs the flow of data between the CPU and other devices
•Sends memory read and write requests to the main memory on the control bus, as well as other commands and control signals such as bus requests, bus grants interrupt requests, etc
What does the Program Counter (PC) do?3
•Holds the address of the next instruction to be executed
•This could be:
•the next instruction in a sequence of instructions
•the address to jump to if the current instruction is a command to jump or branch this would be copied from the CIR
•At the start of a FDE cycle it copies the address and sends it to the MAR
What does the Memory Address Register (MAR) do?2
•This holds the address of the memory locations from which data or an instruction is to be fetched or to which the data is to be written.
•Sends these addresses to memory down the address bus.
What does the Memory Data Register (MDR) do?2
•Used to temporarily store the data which is read from or written to memory
•All data to and from memory must travel down the data bus and pass through the MDR
What does the Current Instruction Register (CIR) do?3
•Holds the current instruction being executed
•The contents of the MDR are copied to the CIR if it is an instruction
•Contains the opcode and operand(s) of the current instruction
What does the Arithmetic Logic Unit (ALU) do?5
•Performa arithmetic and logical operations on data
•Arithmetic operations fixed and floating point numbers: add, subtract, multiply and divide
•Bitwise shift operations left and right
•Boolean logic operations: comparison, and, or, not and xor
•Often uses general-purpose registers to temporarily hold the results of calculations such as the ACC
What does the Accumulator (ACC) do?3
•One of a number of general-purpose registers
•Data or control information is often stored in them
•The results of calculations carried out by the ALU can be temporarily stored here
What does the Address Bus do?1
Carries memory address that identify where the data is being read from or written to
What does the Data Bus do?1
Carries the binary that makes up the actual information being transmitted around the CPU/computer
What does the Control Bus do?1
Carries command and control signals to and from every other component of the CPU/computer
What are the 3 factors effecting the CPU?
• Clock Speed
• Cashe size
• The number of Cores
How does the clock speed determine the performance of the CPU?
The clock speed determines the number of instructions that the CPU can execute per second. (Measured in hertz Hz)
How does the cashe size determine the performance of the CPU?2
• The size of the cashe will affect the amount of data or instructions can be stored temporarily.
• The more that can be stored means the less the CPU needs to return to main memory to save time.
How does the number of cores determine the performance of the CPU?
A CPU with multiple cores will have the ability to run multiple programs at one time.
