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Architecture of CPU, CPU performance, Embedded Systems
Hardware
machines, wiring, physical components of a computer
e.g. mouse, keyboard, circuit board, writing
Software
the programs & other operating info of a computer
e.g. notepad, chrome, files
RAM
Random Access Memory
volatile storage - retains no data when turned off
holds data that is currently being worked on
very fast as no permanent data is being held
CPU
Central Processing Unit
where instructions are processed
circuits that contain lots of transistors
works with memory
Computer system
system that accepts an input, processes it, turns it into an output
storage is needed to hold input & output
hardware & software allow this to happen alongside other components
Computer architecture
the design of a computer system and the different components in it
Von Neumann architecture
modern computers use this architecture
designed by john von neumann
common instructions are stored in memory alongside data (stored program concept)
makes computers more versatile
Stored program concept
instructions & data are stored as binary digits
instructions are fetched from memory one at a time in the order they’re sent
the processer decodes the instruction before executing it
Control unit
understands instructions
tells other components what each instruction needs from them
coordinates all parts and makes sure they’re all working together
ALU
Arithmetic Logic Unit
calculator of the CPU
handles maths & logical operations
Cache
very fast memory in CPU
stores frequently used instructions
reduces need for RAM
Registers
very small, very fast memory location in CPU
MAR, MDR, CIR, PC, ACC
MAR
Memory Address Register - stores memory addresses used when searching for data in RAM
MDR
Memory Data Register - stores data when fetched from MAR
CIR
Current Instruction Register - stores data that is currently being worked on
PC
Program Counter - points to the next instruction to be fetched and increments each time. keeps track of instructions
ACC
Accumulator - stores the result of a calculation
Fetch-execute cycle steps
Fetch: next instruction & any data involved is fetched from main memory
Decode: instruction is decoded
Execute: instruction is carried out
Clock speed
cycles per second in hertz (Hz)
the higher the clock speed, the faster it can process instructions
1 cycle a sec = 1 Hz = one instruction per sec
Number of cores
the number of processors linked together on a single chip
having multiple means that different instructions can be processed simultaneously
dual core processer = 2 processors linked together ect
Cache size
how big the cache is
Three things that affect CPU performance
clock speed
number of cores
cache size
Clock
regular electronic pulse that synchronise the stages of the cycle
basic unit of time in CPU
each fetch execute cycle takes one clock cycle to complete
Embedded system
a specialised computer system that completes a specific task
has all the elements of a typical system
doesn’t have an operating system because it only does a few tasks
built into object/device that it controls - a mini computer system inside it
Where are embedded systems held
ROM (permanent memory)
Example of embedded systems
Washing machine
input is the time, temp, type of wash that the user chooses
system takes that and runs the machine
output could be a noise made/display shown to signify that it’s finished
(other examples: microwave, satnav, home security systems)
ROM
Read Only Memory
non-volatile - data is retained when power is off
used for BIOS and bootstrap
BIOS
Basic Input Output System - checks that hardware is working
Bootstrap
the first code that is executed when the computer system is started
Properties of an embedded system
small
use less power than general-purpose computer
lower cost
Note 
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