1.1 Processors Flashcards
Structure and function of processors Types of processors Input, Output and Storage Devices
What does the Arithmetic and Logic Unit do?
- Handles data processing, performs standard arithmetic operations as well as logic operations and comparisons.
- Completes all the arithmetical and logical operations.
What is the Control Unit?
- Controls the way the data moves around the CPU - controls buses and flow of data between CPU and other components.
- It executes the instructions given by a program.
- A part of the processor which directs operations inside the CPU.
What are registers?
- Quick, small stores of data within the CPU.
- Small memory cells that operate at high speeds.
What does the Program Counter do?
- Holds the memory address of the next instruction.
- Increments by 1 after each fetch stage.
Which register does all the calculations?
The accumulator
What does the MAR do?
- Holds the memory address of the data needing to be accessed
- Holds address of a location that is to be read from or written to
What does the MDR do?
- Holds the data being transferred to or from the memory location by the CPU.
- Temporarily stores the data that has just been read from or the data needs to be written.
What does the CIR do?
- Contains the current instruction during processing.
- Holds the current instruction divided up into opcode and operand.
What is a Bus?
- Parallel wires which connect 2 or more components together.
(The width of the bus is the number of parallel wires a bus has. Directly proportional to the number of bits transferred)
What is the system bus?
The collection of the data bus, address bus, and control bus is called the system bus.
What is the data bus?
- Bidirectional
- Transports data and instructions between components (to and from memory)
What is the control bus?
- Bidirectional
- Carries commands from the CPU & status messages from other hardware devices.
What does the address bus do?
- Unidirectional (only goes from memory to the CPU)
- Transmits the memory address specifying where data is to be sent from or retrieved from.
What does adding a wire to the address bus do to the number of addressable locations?
- It doubles the amount of addressable locations
What does the Bus request indicate?
- indicates a device is requesting access to the data bus
What does Bus Grant indicate?
- Shows that the CPU has granted access to the data bus.
What does memory write do?
- Data is written into addressed location from the data bus.
What does memory read do?
- Data from the addressed location to be placed onto the data bus.
What does the interrupt request control signal indicate?
- Shows that a device is requesting access to the CPU.
What is the clock control signal used for?
- Used to synchronise all the operations/instructions.
What is Assembly Language?
Assembly language is a programming language where mnemonics are used to represent instructions.
What is opcode?
- Part of the instruction code that tells the processor what to do.
What is the operand?
- Contains the data to be acted on, or the memory location of the data in a register.
Describe the Fetch stage.
- The address from the PC is copied to the MAR
- Instruction held at that address is copied to the MDR by the data bus, simultaneously the contents of the PC is increased by 1
- The value of the MDR is copied to the CIR
Describe the Decode stage.
- The contents of the CIR is split up into opcode and operand.
Describe the execute stage.
- The opcode is executed on the data.
What is the clock speed?
- The number of cycles completed per second.
What is cache memory?
- CPU’s onboard memory which is accessed a lot quicker than main memory. Smaller in size but quickest.
What is pipe-lining?
- Fetching an instruction whilst the prior one is being decoded and the one before is being executed.
What is Von Neumann architecture?
- There is a single shared memory and shared data bus for both data and instructions.
What is Harvard architecture?
- Separates the data and instructions into separate memories and data buses for each. The memories can be different sizes making speed a priority.
What is contemporary processing?
- Procesing style in which Von Neumann architecture is used for main memory. Cache uses Harvard architecture, divided into instruction cache and data cache.
Advantages of Von Neumann
- Cheaper to develop as the CU is easier to design.
- Programs can be optimised in size.
Advantages of Harvard architecture
- Quicker execution as data and instructions fetched in parallel
- Memories can be different sizes, makes more efficient use of space.
Disadvantages of Harvard architecture
- More physical space is needed since there are 2 buses. Handling 2 blocks of memory is more complex.
What does RISC mean?
- Reduced Instruction Set Computer
What does CISC mean?
- Complex Instruction Set Computer
What are the properties of RISC?
- Small instruction set
- Each instruction is one line of machine code
- Used in everyday devices.
What are the properties of CISC?
- A large instruction set
- Instructions are built into hardware
- Used in embedded systems and microprocessors.
What are the benefits of RISC processors?
- Pipe-lining is possible since each instruction takes one clock cycle.
What are the benefits of CISC processors?
- Compilers have to do less work
- They require less RAM since instructions are smaller.
What is a graphics processing unit?
- A co-processor made up of lots of independent parallel processors.
What are GPU’s used for now?
- GPU’s are used for image processing and machine learning.
What are multi-core systems?
- Systems where there are multiple cores that separate FDE cycles.
What are parallel systems?
- Systems where multiple instructions can be completed at any given time, doesn’t require multiple cores. it can use threading and pipe-lining instead.
Give two types of magnetic storage
- Hard disk drive
- Floppy disk
- Magnetic tape
Give three examples of input devices
- Keyboard -Touchpad
- Mouse -Barcode reader
- Microphone
- Webcam
Give an example of a device that is both input and output
- Touchscreen
What name is given to the areas on a CD’s surface which have been burned into grooves by a laser?
- Pits
What does CD stand for?
- Compact Disc
Give three examples of output devices
- Speaker
- Monitor
- Printer
- Projector
Order these from highest storage capacity to lowest:
DVD, CD, Blu-Ray
Blu-Ray, DVD, CD
In a hard disk drive, what is mounted at the end of the actuating arm?
Read/write head (needle)
Which storage device has typical capacities in the range 500GB-5TB?
Hard disk drive
Give two disadvantages of SSDs
- Higher cost per GB
- Limited lifespan
What does ROM stand for?
- Read only memory
Describe the structure in which information is stored in flash memory
- Information is stored in blocks, which are combined to form pages.
What is meant by non-volatile?
- Storage medium doesn’t lose its information when power is lost.
Which two types of logic gates are used in flash storage?
- NOR
- NAND
Give two advantages of SSDs
- Higher transfer speeds
- Lightweight
- No moving parts
Is ROM volatile or non-volatile?
- Non-volatile
Which form of storage device uses silicon semiconductors to store information?
- Flash
Give two disadvantages of CDs
- Easily damaged by scratches
- Relatively low capacities
- Slow transfer speeds
