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Overiview of Computer systems - Coggle Diagram
Overiview of Computer systems
What is a computer
Microsprocessor
Wire thickness that was used in LSI
LSI
Large Scale Integration
Process of putting thousands of components onto a singular chip
First Micorprocesors used using LSI
Intel 4004 - electronic calculators
Intel 8008
Intel 8080
Motorola 680
market grows quickly
hobbyists
Compare with previous generations
Minicomputers were massive
mainframes filled rooms
Consumed lots of power
Componenets
System Bus links CPU to components
Random Access Memory holds instructions and data to be accessed by CPU
CPU executes instructions and transforms data
Building Blocks
Change in electrical voltage conveys information
relative to supply voltage
thermonic valves
required supply volatge of 100s volts
electromechnaical relays
used relays (12 - 24 volts)
TTL (Tranisistor - Transistor logic) required 5 volts. Is still used
VLSI (Very Large Scale Integration) 1.2 to 3.3 volts.
Information extracted from this compared to voltage level is called logic levels
Something is either rtrue or false (high or low)
High is 70% or more of voltage
Low is 30% or lower
Voltage level signals on or off information
Voltage levels are fast but have a finite speed
90% speed of light
27cm per nanosecond
electrons push each other along a conducting wire
Flow of electrons is comparatively slower
Needed for switching components between high and low levels
small components need less work so can switch faster
Volatge levels create waste heat. So it needs to be balanced by sometimes using smaller voltages
Digital pulses are the basis of communication on system buses and other circuits
Frequency of pulses are measured in hertz
Gigahertz are commonly used now
Pulses have rising and falling edges
either or both can be used in signalling
Synchronisation
precise timing is needed fro correct operations
Controlled by clock pulses
Drive computation
Greater frequency, the greater the power requirements and waste heat generated
Generated by crystal oscillator with a precise frequency (14.318 megahertz for personal computers)
Subsequent stage is a PLL (Phase Locked Loop) multiplies or divides this frequency as required.
One oscillator feeds many PLLs can generate clock frequencues from a single source which are synchronsied
Different parts of a machine operate at different frequencies
Operate in their own clock domains
Interfacing between different clock domains requires buffer curcuits that hold information long enough for both sides to handshake information being received
Physical size of componenets constrains speed at which it operates
multiple clock frequencies are used which results in multiple clock domains in side a typical computer
clock frequencies are 1 - 5 GHz for CPUs, 200 MHz - 4GHz for RAM, 100 - 200 MHz for buses
higher frequency = better performance, but a bigger power consumption
Peripherals
IO (Input Output) is how you get information in and out of the outside world
performed by peripheral devices
Meaning they were once physically distant from the CPU
Perform various input and output functions
USBs are peripheral
method of accessing other peripherals
Any device other than the CPU, Bus or RAM
Usually hardware