1.1: The characteristics of contemporary processors, input, output and storage devices

Central Processing Unit (CPU)
The CPU contains the ALU, CU, MDR and MAR which are all registers that process data and instructions.
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Memory Address Register (MAR)
This register is used to store the memory address of the next instruction to be used.
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Memory Data Register (MDR or MBR)
This register acts as a buffer and holds anything that is copied from memory ready for the processor to use it.
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Current Instruction Register (CIR)
This register holds the instruction whilst it is being executed.
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Program Counter (PC or SCR)
This register stores the address of the next instruction to be accessed and after an address is copied from here into the MAR, the PC is incremented by 1.
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Arithmetic Logic Unit (ALU)
This processes data by arithmetic operations and logical operations, and also holds the ACC.
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Accumulator (ACC)
This register stores the result of all calculations and all inputs and outputs from the processor pass through here.
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Control Unit (CU)
This contains circuity which controls how all parts of the CPU function by providing timing and control signals.
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Address Bus
This unidirectional bus transports memory address which the processor wants to access in order to read or write data.
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Data Bus
This bidirectional bus transfers instructions coming from or going to the processor.
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Control Bus
This bidirectional bus transports orders and synchronisation signals coming from the control unit and travelling to hardware components.
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A small storage location within the CPU used for storage with no other functions.
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Von Neumann Architecture
A processor architecture which follows a linear sequence of fetch-decode-execute. Memory holds both data and instructions which allows for self-modifying code.
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Harvard Architecture
A processor architecture where there is separate storage and signal pathways for instructions and data meaning the CPU can read an instruction and perform a memory access at the same time.
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Single Instruction, Multiple Data (SIMD)
The processor carries out a single instruction on many items of data (e.g. payroll program).
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Multiple Instructions, Multiple Data (MIMD)
The processor carries out multiple instructions on many items of data using multiple cores.
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Reduced Instruction Set Computer (RISC)
A RISC uses simple hardware, is further from high level languages, has longer code requiring more RAM and every operation takes place in once clock cycle.
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Complex Instruction Set Computer (CISC)
A CISC has more complex hardware, is closer to high level languages, has shorter code requiring less RAM, and some instructions can take multiple clock cycles.
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Pipelining overlaps the three phases of the von Neumann architecture to prevent registers from being idle. This ought to speed up processing by up to 3x unless the next instruction in the pipe is not the next one needed.
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Multi-core Processor
Multi-core processors increase the number of logical units and registers, by fitting multiple cores on a single processor socket which run in parallel.
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The processor can re-order, pipeline, and split instructions into micro-instructions on machine-instruction level. This is required for time sensitive applications.
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Thread-level Parallelism
Thread level parallelism is a measure of how many of the threads in a computer program can be performed simultaneously.
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A multiprocessor is any computer with several processors (each CPU has its own socket).
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The physical parts of the computer system.
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Input Devices
This provides a direct connection between the physical world and the microprocessor.
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Examples include QWERTY, numeric and musical.
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Pointing Devices
Examples include mice, tracker-balls, touch-pads and glide-pads.
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Barcode Readers
A laser scanner reads reflected laser light from a series of dark and light coloured lines. Different widths of lines make up a code that can be converted into a number which allow for faster and more accurate data entry.
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This converts a document into a series of pixels and the larger the number of pixels, the better the definition of the final picture.
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Magnetic Ink Character Reader (MICR)
These are characters readable by humans and computers and are 100% accurate when read.
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Optical Character Reader (OCR)
This reads text directly from the document and measures reflected light to determine character shapes and compares them with memory.
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Optical Mark Reader (OMR)
This recognises the presence of a mark on paper by light reflection and the position of the mark on the paper, printing with a special type of ink, conveys information to the machine.
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Output Devices
A type of hardware which display the results of the computer's processing of data inputted.
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There are in colour or monochrome and the more pixels they have, the better the picture.
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Input or output devices where information is output to the screen with which the user can interact and enter data.
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Dot Matrix Printer
Pins strike at the surface of the paper where multiple copies can be obtained using carbon paper, but are slow, produce poor quality, are noise and cannot print in colour.
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Inkjet Printer
Ink is sprayed onto paper and they are in better quality and in colour, but cartridges need to be frequently changed, there is a low amount of copies per minute, and cannot hold a lot of paper at a time.
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Laser Printer
Powdered ink is fused onto paper by heat and pressure, which have a higher copy per minute then inkjet printers, but the printers themselves are expensive, bulky and heavy.
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A motor which carries out physical processes in the real world.
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Devices or media used to keep information available for later use.
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Magnetic Storage
This is data stored using magnetic polarities with each one either a zero or one. A read-write head is able to detect and modify magnetisation of the material.
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Optical Storage
Data is stored using pits (binary 0) and land (binary 1) and is read using a laser.
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Solid State Storage
An SSD uses microscopic electronic switches to store data, where millions of transistors are either on or off which represents binary data being stored.
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Used to store information within a computer where each part has a separate location referred to using a memory address.
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Read Only Memory (ROM)
Non-volatile memory whose contents are not lost when the machine is turned off.
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Programmable ROM (PROM)
Programmed after manufacture and once programmed cannot be changed.
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Erasable Programmable ROM (EPROM)
Physical links can be altered to store data and the PROM can be reset by exposing it to UV light.
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Electrically Erasable PROM (EEPROM)
The chip does not need to be taken out in order to reset it and can just be done electronically.
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Random Access Memory (RAM)
This is volatile memory whose contents are lost when the machine is switched off.
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Dynamic RAM (DRAM)
This is commonly used in main memory where a logical 1 is used to charge a capacitor, and a 0 to discharge it, and needs to be constantly refreshed to prevent discharging.
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A flip-flop is an electronic circuit with two different states used to store information.
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Static RAM (SRAM)
Each bit is represented by a flip-flop and the output is maintained until it is altered. SRAM takes up more space than DRAM, but is faster and more energy efficient.
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Non-volatile RAM (NVRAM)
RAM whose contents are not lost when power is lost.
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Extended Data Output RAM (EDORAM)
A type of RAM which improves the time to read from memory on faster microprocessors.
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Synchronous DRAM (SDRAM)
The processor and memory are in step with each other, which eliminates some operations required to communicate between the two.
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Double Data Rate SDRAM (DDR SDRAM)
Similar to SDRAM but could theoretically transmit data at the rise and fall of the clock.
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Cache is a faster type of memory than found in main memory as it takes less time to access it.
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Virtual Memory
This uses a portion of the hard disk as extra memory which is slower then using RAM. This is useful when the programs and data in use are bigger than the main memory's capacity.
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Other cards in this set

Card 2


This register is used to store the memory address of the next instruction to be used.


Memory Address Register (MAR)

Card 3


This register acts as a buffer and holds anything that is copied from memory ready for the processor to use it.


Preview of the back of card 3

Card 4


This register holds the instruction whilst it is being executed.


Preview of the back of card 4

Card 5


This register stores the address of the next instruction to be accessed and after an address is copied from here into the MAR, the PC is incremented by 1.


Preview of the back of card 5
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