Hardware and Circuits Flashcards
What is an ADDER
a circuit which carries out all four rules of binary addition.
Made by wiring two half- adders together and adding a third input as well as an OR gate.
what is a HALF ADDER
only carries out the first three rules of binary addition (no carry bit).
XOR gate - sum
AND gate - carry
What is a flip- flop
a “bi- stable” circuit (has 2 stable states)
used to hold a single bit in memory
D - type flip - flop
Holds a signal - typically an input signal. It releases the signal when the clock pulse comes by.
what are the types of inputs and how are they used to plot outputs
Inputs: Data signal and Clock signal
Plot the data level (high or low) at the rising clock signal, and join these to give the output signal.
Which three Components of the Processor are involved in the FDE cycle
RAM
CU
ALU
the CU and ALU are both within the CPU
How are signals passed between the RAM, CU and ALU
Using the Adress bus, Data bus and Control bus
What are Buses?
Communication channels that link parts of the CPU
What is Parallel transmission and where is it used?
Bits are sent together along parallel channels. THis is faster but requires extra space.
Used within the CPU
What is serial Transmission and when is it used?
Bits are sent one after the other, this is slower
Used by USB to connect two devices
Address Bus
Sends adress of a memory location to RAM during fetch and save operations
Data Bus
Sends data and instructions to and from ram during fetch and save operations
Control bus
Sends control signals from the CU telling other parts of the computer what to do
Registers
Small areas of high speed memory within the CPU
What does the PC/ Program Counter do
- Counts through the lines of the program, storing the address of the next instruction + copying it to the MAR
- Increments by one each cycle
- Can be overwritten using branch commands
MAR
stores the address for fetching or saving data
MDR
stores the data/instructions being fetched or saved. It acts as a buffer as instructions are copied to the CIR
CIR
takes the instruction code from the MDR to be decoded.
Summarise the Fetch phase in terms of processor components
Data and instructions go from the RAM to the CU
Summarise the Decode phase in terms of processor components
The CU turns the code into a control signal which is sent to the ALU
Summarise the Execute phase in terms of processor components
the ALU carries out the command
Describe the Fetch phase of the FDE Cycle
-The address of the next instruction is copied from the PC to the MAR
- A read signal is sent via control bus
-the contents of the MAR are sent accross the address bus to RAM
- the instruction held at that address is copied to the MDR by the data bus. Simultaneously, the PC increments by 1.
- The contents of the MDR are copied to the CIR
Describe the decode phase of the FDE cycle
- within the CIR, the instruction is split into an operator and operand
- it is decoded and turned into a control signal, which is sent from the CU to the ALU via control bus
Describe the Execute phase of the FDE cycle
- The appropriate instruction is carried out on the operand in the ALU
- The result is stored in the accumulator.
How is the result of an operation saved?
The ALU copies the result to RAM
How are data and instructions stored in Von Neuman Architecture?
Together in RAM as binary numbers
How are data and instructions stored in Harvard Architecture?
RAM is split into 2 partitions for data and instructions to be stored seperately
How are data and instructions stored in Contemporary/ Modern Harvard Architecture?
Together in RAM as binary numbers
How many buses are used for data and instructions in Von neuman architecture
has a RAM, CU and ALU joined by buses
There is one bus used for data and instructions (the data bus)
Therefore it takes 2 FDE cycles to complete a command
How many buses are used for data and instructions in Harvard Architecture
Two seperate buses
How many buses are used for data and instructions in Contemporary/ Modern Harvard Architecture
Two seperate buses
Compare the three types of processor architecture: Von Neuman, Harvard, Contemporary/ Modern Harvard
Von Neuman: Flexible but slow
Harvard : Faster but Inflexible
Contemporary : Best of both
What is an Instruction Set
a list of all instruction codes known by the processor
what is CISC and it’s attributes
Complex Instruction Set Computer
- Has a large instruction set (some rarely get used)
- each instruction long and detailed
- may take several cycles to carry out an instruction
- only a few lines to write a program
- Requires more power (larger battery)
- Generates more heat (cooling mechanisms)
- More expensive complicated circuits
what is RISC and it’s attributes
Reduced Instruction Set Computer
- Short and simple instruction set
- each code does 1 simple task
- takes ~1 cycle to carry out 1 instruction
- Takes many lines to write a program
- may require greater RAM due to program size
- Requires more complex compiler
- small slim processor
Compare RISC and CISC
- neither is faster than the other
- CISC software cannot be run on a RISC computer
- RISC better suited due to mobile devices due to small size, cheapness, use of less power and less heat produced.
7 factors affecting processor performance
- Clock speed
- Word length (size of bus and registers)
- Cache size
- Amount of RAM
- co - processor/ graphics card/ SIMD
- pipelining
- multi- core/parallel processing / MIMD
what is pipelining
-One instruction is fetched while another is being decoded and another is executed.
- Concurrent processing of multiple instructions
- only works if instructions aren’t dependent
what is parallel processing
the use of a multi - core processor (MIMD) that can process several instructions concurrently.
Can only happen if the instructions aren’t dependent
Which 2 types of computer can’t use pipelining?
- CISC
- Von Neuman
what is SIMD
Single Instruction Multiple Data
the processor fetches and decodes an instruction once, then it carries out the single instruction multiple times, processing many data items in the same way.
what are SIMD sub- processors / co- processing
- a group of small processors carrying out the same instructuon at the same time
- very fast way to process a large amount of data
what is a GPU or graphics card
Specialist hardware add- on that processes images very rapidly using SIMD/ co- processor.
Can be used for other tasks than graphics eg. bitcoin
what is MIMD or multi- core processing
- Multiple instruction , multip;e data
- a group of processors work together, carrying out different instructions.
- a shared block of memory holds the instructions and data
list advantages and disadvantages of MIMD
+ uses less energy
+ generates less hear
+ speed advantage
- task dependency
- complex software design
used in almost every modern computer
list advantages and disadvantages of SIMD
+ fast processing
+ process large amounts of data
- dependencies between data
- varied processes
what is input
conversion of data into digital electronic form prior to processing
list 4 types of input
- user input
- image processing
- digital signal processing
- sensors
when should manual input be used + give an example
- input is varied
- speed not as important as flexibility
- no special equipment available
eg. mouse , keyboard
when should automated input be used + give an example
- input is structured
- input is repetetive
- speed is important
eg. barcode, chip and pin
when should sensor input be used + give an example
- input is detectable by sensors
- must be monitored without breaks
- input takes place where there is no human operator
eg. temperature, pressure
how do input devices convert analogue to digital
- analogue measurements vary continuously. examples include temperature and sound waves.
- input devices sample the value many times a second
- each sample is recorded as a digital value
how to acheive high quality digital recordings from an analogue input such as sound waves.
- sample the signal frequently
- store variations precisely
what does an accelerometer measure
start of a movement, a change in velocity, change in direction of motion.
they can be found in most mobile phones.
what is a RFID
Radio Frequency Identification Tag.
- attatch or implant into products or even living creatures.
- when the chip is scanned you can identify or locate the tag and hence the object.
- an “active” tag also has a battery which broadcasts radio waves
explain how code number size is related to the quality of analogue input and outpit
the bigger the number is, the more precise the stored information is.
eg. 10 degrees vs 10.2 degrees.
what is CAD/ CAM
explain it’s input, processing and output
computer aided design/ manufacture
Input - use 3D toolsets with mouse or touch screen
processing - replace blocks, compare drawings, count objects
Output - 3D print or Display on screen
give 4 attributes of robotics
- combine sensors with actuators
- independent processing
- self- moving
- mostly do not look like humans
what is the difference between memory and storage.
memory: electronic, currently in use
storage: non- electronic, not in use
ROM
read- only memory
used for boot instructions
wired in permenantly at factory
RAM
-volatile electronic memory used in normal operations
- can access any location in one step
Cache
small amount of fast access memory that stores frequently used instructions
Virtual memory
Storage used as memory
Describe Magnetic storage and give a pro and con
magnetic disk coated with iron particles. electricity magnetises the particles. North and south represent 1 and 0.
High capacity but not portable.
Describe optical storage and give a pro and con
a laser burns tiny pits into the surface of a plastic disk
presence or absence of a pit represents 1 or 0
Inexpensive , but can only be written once.
Describe flash or SSD storage and give a pro and con
electrons carry negative charge.
Light, portable, high capacity and fast
but is more expensive
ALU
holds results of calculations from ALU
holds all input / output
