1.1 Systems Architecture Flashcards
What is the purpose of the processor(CPU)?
- Retrieves Data/Instructions from Main Memory (fetch)
- It processes data(decodes instructions)
- Carries out instructions(executes them)
- Stores data into main memory once executed
What are the three busses between the cpu and ram?
- Address bus
- Control bus
- Data
PC
Program counter
MAR
Memory Address Register
MDR
Memory Data Register
ACC
Accumulator
-results of calculations from the ALU are stored in the ACC
ALU
Arithmetic Logic Unit
-performs arithmetic and logical operations including +,-,AND,OR
CU
Control Unit
Memory stored on the CPU?
Cache
RAM
Random Access Memory
CIR
Current Instruction Register
What the fetch part of fetch decode execute?
1) Copy address from PC to MAR
2) Get data from RAM and copy to the MDR
3) Copy from MDR to CIR
4) Increment PC
What the decode part of fetch decode execute?
1) Split opcode from data address in MDR
2) Control unit interprets opcode
What the execute part of fetch decode execute?
1) Data address copied from PC to MAR
2) Get data from RAM and Copy to MDR
3) Instruction executed
What are features of RAM?
- Holds data and instructions that are currently in use by the processor
- Located on the motherboard
- Directly Accessible by the processor
- All data/instructions are lost once power is turned off
ROM
Read Only Memory
What is the ROM?
- instructions are permanently etched onto a ROM chip
- when power is turned off instructions still remain on the ROM chip
- bootstrap loader is held on ROM(it gives the instruction to start up the operating system
EEPROM, examples and function
Electronically Erasable Programmable Read Only Memory
E.g. SIM cards, flash memory
-instructions/data can be erased electronically and replaced
What is a bus?
A bus is a set of parallel wires connecting two or more independent components of a computer system in order to pass signals between them
What does the address bus do?
- carries addresses from the processor to main memory or other I/O devices
- It’s one direction
- the processor generates an address
- all data/ instructions are returned on the data bus
What does the data bus do?
- carries data from main memory(or secondary storage devices) to the processor
- bi-directional
- data can be read/written
What does the control bus do?
-control signals instruct which data will be traveling to/from memory
How does clock speed affect the CPUs performance?
-Processors have a clock speed measured in Hz(cycles per second)
-a 1G Hz Processor executes 1 billion instructions per second
The quicker the clock speed the more instructions per second the processor can do
How does the number of cores affect the performance of a CPU?
Processors can be multi core
Each core executes instruction independently
Dual core may execute up to twice as many instructions per second
