System Architecture Flashcards
What is the purpose of CPU?
The processor is “the brains of a Computer System”
It Processes Data
Carries out instructions (Executes Them)
Retrieves Data/Instructions from Main Memory (Fetch)
Processors have a Clock speed measured in Hertz
Number of Cycles Per Second
What measurement is used to assess the speed of CPU?
MHz and GHz
How many instructions can 1 GHz can execute per second?
1 Billion
What is a core in processor?
Core, is where the instructions get processed.
Processor can be multi-core, what are the common terms used for these?
Dual core, Quad core, 8 cores
What is the advantage of dual core over single core processor?
Dual Core may execute up to twice as many instructions per second
What is cache memory?
This is a small memory chip inside the processor.
It acts as an intermediary between the processor and the Main Memory
As programs are executing – the Cache holds commonly used instructions
What affects the performance of CPU?
Clock speed, Cores, Cache size
What is an embedded system?
A computer System that is made up of both Hardware and Software
Usually for very specialised tasks
Doesn’t usually contain an Operating System
An example: Dishwasher
What are the internal components of a computer?
The processor
Main memory
I/O controllers
Buses
What are the external components(Peripherals) of a computer?
Keyboards, Mouse, Printer, disk drives
|I/O devices, I/O ports
Secondary Storage
What is RAM?
RAM – Random Access Memory
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
What is ROM?
ROM – Read Only Memory
Instructions are permanently etched onto a ROM Chip
When power is turned off – instructions still remain on the ROM chip.
Bootstrap Loader is held in ROM
Gives the instructions to start up the Operating System
What are I/O controllers?
These are used to allow an interface between a hardware device external to the motherboard (e.g. a Keyboard) and the Processor itself.
I/O controllers are used for:
Keyboard, Mouse, Disk Drive, VDU
What are System Busses?
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.
The System is split into three separate busses:
The data bus
The address bus
The control bus
What does address bus do?
Carries addresses from the Processor to main memory or other I/O devices
It is one direction (Uni-Directional)
The processor generates an address
All data/Instructions are returned on the Data Bus
What does data bus do?
Carries Data/Instructions from Main Memory to the Processor (or from other secondary storage devices) to the processor.
Bi-Directional (two way)
Data can be read/written
What does the control bus do?
Control signals are sent along the control bus
E.g. Memory Read, Memory Write
This instructs which was data will be travelling to/from memory.
What are Peripheral devices?
Peripherals are any devices that are not directly connected to the CPU
E.g. mouse, keyboard, printer, hard disk drive, cd-rom drive
These devices are known as I/O devices (Input/Output Devices)
What are I/O ports?
I/O Ports allow communication from an I/O device and the motherboard (hence CPU)
Process registers:
What does PC-program counter do?
Holds the location of the next instruction/data address in Main Memory
What does MAR – Memory Address Register ?
The contents of the PC are copied here and then transferred along the Address Bus
What does MDR – Memory Data Register
Once Data/Instructions are brought from the Memory Address in Main Memory – they are placed in the MDR.
What does CIR – Current Instruction Register do?
The instructions stored in the MDR are copied here
What happen in Fetch, decode and execute cycle?
Decode / Execute Part
The instruction to be decoded is held in the Current Instruction Register
The instruction is split into an Op-Code and an Operand
The instruction is carried out by the ALU (Arithmetic Logic Unit)
What is ALU function?
Performs arithmetic and logical operations including +, -, AND, OR
What does register Accumulator holds?
Results of calculations are placed into the Accumulator
