Unit 1.1 Flashcards
What does CPU stand for?
Central Processing Unit
What is the purpose of the CPU?
The purpose of the CPU is to fetch instructions from RAM, decode them and execute them. It may process data in the ALU and may store data in RAM once the instruction is executed.
What process does the Von-Neumann architecture follow?
follows a linear process – FETCH/DECODE/EXECUTE
What does the Von-Neumann architecture consist of?
This architecture has a single processor which retrieves instructions and data from memory (RAM)
Has: PC, MAR, CU, CIR, MDR, ACC, ALU, address bus, control bus and data bus connected to RAM
What is a register on the CPU?
A register is a small block of memory to hold data, normally about 4/8 bytes, which is used in order for instructions to be processed.
What does PC stand for?
Program Counter
What does MAR stand for?
Memory Address Register
What does MDR stand for?
Memory Data Register
What does ACC stand for?
Accumulator
What does CIR stand for?
Current Instruction Register
What is the purpose of the PC?
Stores the memory address of the next instruction. Is incremented by one after an instruction is fetched.
What is the purpose of the MAR?
A special purpose register which stores the address of the next instruction or data to be fetched into the CPU. This is where the address that was read by the PC is sent.
What is the purpose of the MDR?
A special purpose register which stores the data fetched using the address found in the MAR.
What is the purpose of the ACC?
Stores a running total of the calculation that is currently happening.
What is the purpose of the CIR?
Holds the instruction (and associated data) that is currently being implemented – added at the end of Fetch cycle from MDR (because MDR may be overwritten in execute cycle.
What does CU stand for?
The Control Unit
What does ALU stand for?
Arithmetic Logic Unit
What is the purpose of the CU?
Controls the flow of data in the CPU in the fetch execute cycle. Controls the input and output of data so data goes to the correct place at the correct time. Controls and monitors hardware.
What is the purpose of the ALU?
It works out any arithmetic needed. This means it adds, subtracts, multiplies and divides. It works out any logic comparisons e.g. is one number less than another? Is one number equal to another, and so on.
What factors affect CPU Performance?
Processor speed
Number of cores
Cache size
What is the processor speed/clock speed?
Measured in GHz is the number of cycles that can be completed in one second.
How can processor speed/clock speed affect CPU performance?
The higher the processor speed the more quickly the instructions can be processed.
What are the registers on the CPU?
MAR MDR CIR PC ACC
How can the number of cores affect CPU performance?
Multi core processors can carry out more instructions per second than single core. Each core executes instructions independently. Dual Core may execute up to twice as many instructions per second – and so on for quad core…
