Hardware Flashcards
central processing unit (cpu)
processes instructions and data that are input into the computer so that the result can be
output
control unit (CU)
manages other components of the cpu and overall operation (including fetch-decode-execute cycle and ALU)
arithmetic logic unit (alu)
responsible for carrying ou mathematical operation (eh bit shifts)
why dos alu use accumulator (acc)
temporarily store the data while performing calculations
registers
small areas of storage found within cpu (PC, MAR, MDR, CIR, ACC)
pc
program counter - holds the address of the next instruction to be fetched
mar
memory address register - used when reading or writing data from/to ram
mdr
memory data register - used to read/write from/to ram. mdr contains data while mar contains address
cir
current instruction register - holds the instruction which is currently being decoded or executed
acc
accumulator - used to hold data being worked on by alu
bus
way of communicating between components
how many buses does cpu have
3 (control, address, data)
control bus
carries control signals from the control unit to other components of the cpu
address bus
carries addresses from mar to ram to indicate which address will b selected
address bus is
unidrectional
data bus
carries thee data to be written from the mdr to ram
the data bus is
bidirctional
fetch-decode-execute cycle
cycle computer follows to run programs
active computer programs are stored in the
ram
fetch steps
- PC contains the location of the next instruction
- This address is copied to the MAR.
- pc is incremented by 1 so that it points to next instruction
- address bus carries value in mar to ram
- control bus sends read signal to ram
- contents of mdr are copied to cir
decode steps
cu decodes instruction in cir
execute steps
- instruction is sent to alu to be executed
- alu may use acc to temporarily store its results
factors that affect cpu performance
clock speed, cores, cache
clock speed
- determines number the cycles cpu can perform each second (measured in gigahertz)
- higher clock speed -> more heat -> more energy
core
processor within cpu that carries out one instruction at a time
why is a multi core cpu not necessarily an advantage
they run tasks simultaneously however, individual programs have instruction that run in a sequence
cache
fast memory located within cpu used to store temporary copies of data in most commonly accessed ram locations
read operation
To read, the registers MAR and MDR are needed
The address is copied to the MAR
Signal is sent from the processor to the memory
Content is copied to the MDR
write operation
Data is written on the MDR
The address is written in the MAR
A ‘write’ signal is sent from the processor to the memory unit through the CU
what is a microprocessor?
type of integrated circuit
on a single chip
structure of computer that has a
Von Neumann architecture
- units: arithmetic logic unit (ALU) and control unit (CU)
– registers: program counter (PC), memory address register (MAR), memory data register (MDR), current instruction register (CIR) and accumulator (ACC)
– buses: address bus, data bus and control bus
dual core
can work on two instructions t a time (higher CPU speed)
instruction set
list of all the commands
that can be processed by a CPU and the
commands are machine code
add instruction set
add two numbers together
sub instruction set
subtract one number from another
inp instruction set
input data from an input device
out instruction set
output data from an outrput data
load instruction set
load data from RAM
store instruction set
save data to RAM
what is an embedded system
- embedded system is used to perform a dedicated function (e.g. domestic appliances, cars, security systems, lighting systems or vending machines)
- This is different to a general purpose computer that is used to perform many different functions, (e.g. a personal computer (PC)
or a laptop)
