4.7.1 Internal Hardware components of a compute 4.7.2 The stored Program concept Flashcards
Explain the role of the processor?
1) The Processor responds to and processes the instructions that drive the computer
2) It contains the control unit, the arithmetic logic unit (ALU) and the registers
3) The control unit coordinates and controls all the operations carried out by the computer
4) The processor repeats the following operations
- Fetch: Causes nest instruction to be fetched from memory
- Decode: Decodes the instruction
- Execute: Causes the instructions o be executed
What is the function of the ALU?
The Arithmetic Logic Unit (ALU) performs:
1) Addition
2) Subtraction
3) Multiplication
4) Division
What is a bus? (ADC)
A bus is a set of parallel wires connecting two or more components of a computer the processor connects to the main memory via three main busses
1) Address Bus
2) Data Bus
3) Control Bus
What is the address bus?
1) The address bus is used to transport memory location addresses of the register the data is being carried to
2) The width of the address bus determines the maximum possible capacity of the system
What is the data bus?
1) The data bus is bi-directional for carrying data and instructions between the processor and memory
2) Width of the data bus is important towards the overall performance
3) If the bus is 8 bits wide and each instruction is 16 bits wide the processor must access the main memory twice to fetch the instruction
What is the control bus?
1) Bi-Directional bus that carries signals
2) Transmits command timing and specific status information between the system components
What are the I/O controllers?
1) An I/O controller is a device that interacts between an input or output device and the processor
2) The device has a separate controller that connects to the control bus
3) Controllers receive input and output from the processor and then send back specific control signals to the device that they control
What is main memory?
1) Main memory is memory that can be accessed directly by the processor. The main memory consists of memory locations that store instructions or data. There are two types of main memory:
1) volatile memory, which loses its contents when the power is removed
2) non-volatile memory, which keeps its contents even without power
Usually refers to RAM (random access memory) which is a volatile memory
What is the Von Neumann architecture?
1) This architecture specifies the basic components of the computer and processor in which a shared memory bus is used for both data and instructions
2) Makes use of the stored program concept where machine code instructions are fetched and executed serially by a processor that performs arithmetic and logical operations
3) This architecture is used extensively in general-purpose computing systems
What is the Harvard architecture?
1) A computer architecture with physically seperate memories for instructions and data
2) Used in embedded systems such as Digital processing systems (DSP)
What is the difference between the Von Neumann and Harvard architectures?
1) Harvard architecture is faster than Von Neuman as data and instructions are fetched in parallel rather than competing for the same bus
What is the function of the control unit?
1) The Control unit controls and coordinates the activities of the CPU directing the flow of data between the CPU and other devices
2) It accepts instructions, breaks them down into sequential steps, manages execution and stores the result in memory and registers
What is the System clock?
1) Generates a series of signals between 0 and 1 billion times a second
2) Synchronizes CPU Operations
3) E.g. A 3GHz processor’s clock ticks three billion times per second
4) Operations start as the clock changes from 0 to 1 and the CPU cannot perform operations faster than the clock cycle
What are General Purpose registers (Accumulator) ?
1) 16 registers in a CPU
2) All arithmetic, logical and shift operations occur in registers
3)
- Load contents of 150 into R1
- Add contents of 164 to R1
- Store contents of R1 to 170
4) Also known as a accumulator
What is the program counter (PC)?
1) Hold the address of the next instruction to be executed
2) E.g. Next instruction in a sequence of instructions
What is the Current instruction register (CIR)?
1) Holds the current instruction being executed
What is the memory address register?
1) Holds the address of the memory location from which data (or an instruction) is to be fetched or to which data is to be written
What is a memory buffer register? (MBR)
1) Used to temporarily store the data read from or written to memory
What is a Status register?
1) Contains bits which are set or cleared depending on the result of an instruction
2) E.g. One bit could be set if an overflow occurs
Other bits may indicate whether a result of the last instruction was negative, zero or caused a carry
What is the Fetch-code-Execute cycle?
1) Sequence of operation involved in executing an instruction
2) Divided into 3 sections:
- Fetching
- Decoding
- Executing
3) This cycle is repeated over and over as each instruction of the program is executed
Explain the Fetch phase of the cycle including the registers used? (Step 1)
1) Address of next instruction copied from Program Counter (PC) to the memory address (MAR)
2) Address is sent via the address bus to the main memory
3) The instruction in that address is returned to the memory buffer register
4) At the same time the content of the PC (Program Counter) is incremented to hold the address of the next instruction
5) The content of the MBR is copied onto the CIR (Current Instruction Register)
Explain the Decode Phase of the cycle including the registers used? (Step 2)
1) Instructions inside of the CIR is decoded and split into opcode and operand
2) Opcode used to determine the type of instruction and what hardware is used to execute it
Explain the Execute Phase of the cycle including the registers used? (Step 3)
1) Instructions are executed using the ALU if required
2) The results are stored in the accumulator, general purpose register or memory
What is meant by processor instruction set?
1) Processor instruction set is processor specific and it is a set of all the instructions that are supported by its hardware
Understand a Barcode Reader?
1) Two different types of barcode linear barcode and 2D barcode
2) 2D barcodes store more information in the same space as a 1D barcode but they require more processing
3) The pattern of light and dark strips in a barcode represents binary 1’s and 0’s
4) Barcodes have error detection such as parity bits and check digits which check if a barcode has been read correctly
Understand a digital camera?
1) A digital camera consists of a lens that focuses light onto a sensor the path of light is regulated by a shutter
2) Two common sensors used are CMOS and CCD which convert incident light into electrical charge
Understand a Laser Printer?
1) A laser printer is an output device that produces images on paper from digital signals
2) Drum +ly charged toner is -ly charged opposites attract
3) Paper is heated by fusers and the toner is fixed to the paper
Understand RFID Radio Frequency Identification?
1) Method of transferring information wirelessly
between a tag and a reader
2) Contains a chip with a small amount of memory and a coil is attached to it which acts as an antenna
3) When an RFID tag is scanned, the reader emits radio waves which are picked up by the
tag’s antenna
What is a Hard Disk?
1) A Hard disk consists of a number of circular platters which are made from a magnetic material. Above each platter hovers an actuating arm on which is a read/write head.
