Components of a computer (unit 1) (finished) Flashcards
(1.1) What is a CPU?
Central processing unit
(1.1)What are some of the components of a CPU?
Control unit
Buses
ALU
Dedicated registers
(1.1) What does the control unit do?
Coordinates the activity of all other components
(1.1) What do buses do?
used for transporting data, tiny wires that transfer signals between components
(1.1)How many different system buses are there, and what are they called?
3-
Control bus- Signals from the control unit to other parts of the processor
Data bus- carries data from one place to another
Address bus- carries location address where the data is going (to or from)
(1.1) What control signals are there?
Memory read Memory write Bus request Bus grant clock
(1.1)What does the ALU do?
Arithmetic logic unit
This component performs arithmetic, logical and shift operations on data
Arithmetic operations: Add, Subtract, Multiply and Divide
Logical operations include: AND, OR, NOT, XOR
Shift operations: Move bits to the left or right within a register
(1.1) What does the ACC do?
Single general purpose register used to store values of recently done calculations
(1.1)What are some dedicated registers used by the processor?
Program counter (PC) – holds the memory address of the next instruction to be executed
Current Instruction Register (CIR) – holds the current instruction, which is split into opcode and operand
Memory Address Register (MAR) - holds the address in memory where the processor is required to fetch or store data from or to
Memory Data Register (MDR) – temporarily holds data moving between the processor and main memory
Accumulator (ACC) – to hold intermediate results of an instruction
(1.1) What is the fetch decode execute cycle? (FDE)
The order in which processors carry out program instructions:
Fetch- retrieves the data
Decode- decodes the data
Execute- carries out the decoded data
(1.1) detailed version of FDE cycle
Fetch:
1.The address of the next instruction is copied from the PC to the Memory Address Register (MAR)
2.The instruction held at that address is copied to the Memory Data Register (MDR)
3.Simultaneously, the contents of the Program Counter (PC) are incremented by 1
4.The contents of the MDR are copied to the Current Instruction Register (CIR)
Decode:
5.The instruction held in the CIR is decoded
6.It is split into operand and opcode to determine the type of instruction it is. Additional data, if required, is fetched from memory…
7.and passed to the accumulator
Execute:
8.The instruction is executed and the result held in accumulator or stored in memory
(1.2) What is a word?
A word is the unit of data that memory is divided into
Word length is usually 8, 16, 32 or 64 bits
(1.2) What is the address bus, and why is it important?
carries location address where the data is going (to or from)
The width of the address bus determines the maximum possible memory addresses of the system
(1.2) What is special about the data bus?
The data bus is bi- directional
(1.2) How close is assembly language to machine code?
Very closely related, usually have a one to one correspondence
(1.2) What are some factors that could affects processor performance?
Clock speed- determines the cycles of FDE per second
Number of cores
Amount/type of cache memory
(1.2) What is a co-processor?
A co-processor is a second, less powerful processor that runs alongside the regular processor
This is uncommon due to the hardware complexity
(1.2) What is parallel processing?
Using several processor cores working at the same time
Each different core can work on a different part of the same task (this isn’t always possible due to some instructions having to be processed sequentially)
(1.2)What are the levels of memory storage in order of speed?
CPU registers
lvl1 cache
lvl2 cache
RAM
(1.2) What sections is lvl1 Cache memory split up into?
Instruction cache and data cache
(1.2)What is pipelining?
Pipelining is the process of overlapping stages in the FDE cycle
One example of this is as soon as one part of the process has been completed for one part, it is started for the part after.
(1.3)Who were the first people to suggest a stored program concept?
John von Neumann and Alan Turing
(1.3)What is the stored program concept?
A program must be loaded into main memory to be able to be reached by the processor (and then executed)
The instructions are fetched one at a time, decoded and executed sequentially/in order by the processor. This is the FDE cycle.
The sequence of instructions can only be changed by a conditional or unconditional jump instruction. This is sometimes called a branch
(data and instructions are both logically the same, which makes them interchangeable.) (von Neumann is built around this principal, which is why they have the same storage space)
(1.3)What is the Von Neumann architecture?
Instructions and data are stored in a common main memory and transferred using a single shared bus
(1.3)What is the Harvard architecture?
Different sized memories and word lengths can be used for data and instructions
Mainly used in embedded systems, where speed takes priority
(1.3)Advantages of the von Neumann architecture
Owing primarily to cost and programming complexity, almost all modern computers are based on von Neumann’s ideas
It is easier to share information with other computers that use the same processing methods
It simplifies the job of the Control Unit
Data from memory and from external devices are accessed in the same way
(1.3)Von Neumann vs Harvard architecture comparison
Von Neumann:
Used in PCs, laptops, servers and high performance computers
Data and instructions share the same memory. Both use the same word length
One bus for data and instructions is a bottleneck
One bus is simpler for control unit design
Harvard:
Used in digital signal processing, microcontrollers and in embedded systems such as microwave ovens and watches
Instructions and data are held in separate memories which may have different word lengths. Free data memory can’t be used for instructions, and vice versa
Separate buses allow parallel access to data and instructions
Control unit for two buses is more complicated and expensive
(1.3)Which architecture do current processors use?
Current processors use a mixture of both von Neumann and Harvard architecture, such as there being one main memory for data and instructions, but cache is divided into an instruction cache and a data cache.
(1.3) What are some features of the Von Neumann architecture?
(Single) Control Unit
(Single) Arithmetic Logic Unit
(Special) registers within CPU
Instructions and Data stored in same area of memory
Instructions and Data stored in same format
A single set of buses / same bus for instructions & data (to connect CPU to Memory and I/O)
(1.3) What are some features that a contemporary processor might have, that are not part of the von Neumann architecture?
Two separate areas of memory… one for instructions & one for data.
Different (sets of) buses… one for instructions & one for data.
Pipelining… whilst an instruction is being executed the next can be decoded and the subsequent one fetched.
Use of Cache… A small amount of fast memory next to the CPU
Multiple Cores… Each core acts as a separate processing unit.
Onboard Graphics… Built in circuitry for graphics processing.
(1.3)What is CISC?
Complex Instruction Set Computers (CISC)- individual instructions may perform many operations and take many cycles to execute, in contrast with reduced instruction set computer (RISC).
(1.3)What is RISC?
Reduced Instruction Set Computers (RISC)- utilizes a small, highly-optimized set of instructions rather than the highly-specialized set of instructions typically found in other architectures.
A minimum number of very simple instructions, each taking one clock cycle, are used to accomplish all the required operations in multiple general purpose registers
(1.3)What are some advantages of CISC and RISC
CISC:
Quicker to code programs
The compiler has very little work to do to translate a high-level language statement into machine code
Because the code is relatively short, very little RAM is required to store the instructions
RISC:
The hardware is simpler to build with fewer circuits needed for carrying out complex instructions
Because each instruction takes the same amount of time, i.e. one clock cycle, pipelining is possible
RAM is now cheap, and RISC use of RAM and software allows better performance processors at less cost
(1.3)What is an advantage of using a RISC processor over a CISC processor?
Advantage is Costs less to design/produce.
because
- Requires less cooling to be built in.
- (If battery powered) can run off smaller battery.
- Has fewer instructions than other (CISC) processors.
- Simpler (circuit/hardware) design/manufacture.
- Fewer transistors.
(1.3)What are muti-core processor systems?
Systems that are able to distribute their workload over multiple processor cores, and therefore using parallel processing/ becoming parallel systems.
(1.3)When is parallel processing useful?
The software has to be written to take advantage of multiple cores
For example, browsers such as Google Chrome and Mozilla Firefox can run several concurrent processes
Using tabbed browsing, different cores can work simultaneously processing requests, showing videos or running software in different windows
(1.3)What is a GPU, and why does it improve a PC’s performance?
A Graphics Processing Unit (GPU) is a specialised electronic circuit which is very efficient at manipulating computer graphics and image processing
In a PC, a GPU may be present on a graphics card, and takes away all the graphics processing jobs from the CPU
(1.3)What is a co-processor?
A co-processor is an extra processor used to supplement the functions of the primary processor (the CPU)
(1.4)What is an input device?
input device is a piece of equipment used to provide data and control signals to an information processing system
(1.4)What types of input devices are there?
Manual- done by user
Automatic- done by devices/ scanners
(1.4)Can you name some input devices?
Mouse Keyboard Camera track pad interactive whiteboard microphone scanner
(1.4)What is a QR code?
QR codes are 2D barcodes and can be read by smartphones or tablets
(1.4)What is a sensor, and can you name some?
A hardware device that can take measurement of physical properties, such as temperature or pressure, from real world surroundings. These measurements are usually a representation of the actual property being measured.’
Sensor types: Gas (e.g. oxygen, carbon dioxide) Infra-red (e.g. motion or heat source) Light Temperature Pressure pH (i.e. acid or alkalinity) Magnetic field Moisture/humidity Acoustic (i.e. sound)
(1.4)What is an Analogue measurement?
Analogue means that data has no discrete value and the data changes smoothly rather than in exact jumps
(1.4)Difference between a Monitoring application and Control application
Monitor:
Records the values, but can’t make changes to how the process is running
Control:
Can make changes to the process based on how the process is running
(1.5) What is an output device?
An output devices take data produced by a computer and turn it into a human-readable form (such as a printed document or an image on a screen)
(1.5) What are some common output devices?
printers, screens, loudspeakers and multimedia projectors
(1.5) What types of printer are there?
inkjet printer
dot matrix printer
laser printer
3d printer
(1.5) How do speakers work?
Digital data is sent from the computer to a Digital to Analogue Converter (DAC) where it is converted into an analogue signal
The signal is then boosted using an amplifier and finally sent to a speaker
(1.5) When are inkjet printers used?
Producing one off high quality documents
printing labels directly onto a cd
Used for professional photograph printing
(1.5) When are Laser printers used?
Businesses use almost exclusively laser printers because they are fast and reliable
Print quality is excellent
Common uses include printing company stationery making labels creating brochures fliers
(1.5) When are dot matrix printers used?
Useful where multi-part stationery is required
Can work effectively in damp or dirty atmospheres
(1.5) When are 3d printers used?
Used to create 3d models, much more difficult to work with
(1.5) What are the different types of monitors?
LCD- Liquid crystal display
LED-Light emitting diode
CCFL- Cold cathode florescent lamp
OLED- Organic light emitting diode
(1.6) What are the two main types of storage?
RAM- random access memory
ROM- read only memory
(1.6) What are the main differences between RAM and ROM?
RAM:
what is stored in it- operating system, Running programs, Data currently being used
what happens when it is turned off- lost (volatile)
can you read and write to it?- yes, read and write
Rom:
what is stored in it- Computer bootup instructions (Bootstrap)
what happens when it is turned off- retained (non-volatile)
can you read and write to it?- read only
(1.6) Why is ROM special?
Rom is special because some instructions need to be held permanently, even when the power is off, and so are stored in ROM
(1.6) What happens to the RAM in a computer when it is turned off?
RAM is emptied, as it is volatile
(1.6) What is loaded into RAM when the computer boots up?
OS- operating system
(1.6) What happens to RAM as you open more programs, and what happens when it is full?
RAM starts filing up
When it is full it overflows into virtual memory
(1.6) What are the 3 main primary storages?
RAM
Registers
Cache
(1.6) What are the 3 types of secondary storage?
Magnetic- hard disk
optical- CD-ROM
Solid state- flash memory
(1.6) What are some of the differences between secondary storage devices?
Durability Read / write speed Capacity Portability and Cost
(1.6) What are some advantages and disadvantages of solid state devices?
More durable
Faster than hard disk drives
Consume less power
More portable
More expensive than hard disk drives
Typically less capacity than a hard disk
(1.6) What are some uses for optical disks?
CD-ROM is widely used for software distribution
CD-R may be used for copying a game, software, audio or video files or documents. These can then easily be stored offline
CD-RW useful for short- or medium-term backup, or transferring files from one computer to another
DVD and BluRay are high-capacity discs which can store feature-length films
(1.6) What are some advantages and disadvantages of magnetic devices?
Cheap Storage per MB (especially tape drives!)
Relatively quick read / write speeds.
Easily broken if dropped
Slow read /write compared to new SSD drives.
High energy uses as it uses moving parts (lower battery life on laptops)
(1.6) What are some advantages and disadvantages of optical devices?
quite portable
Very Low cost
Low Capacity
Very Slow Read / Write speed
Easy to scratch and data loss easy
Not very reliable
(1.6) How can CDs, DVDs and BluRays differ in capacity if they are all the same size physically?
Different laser wavelengths burn smaller pits, meaning that the smaller the track the tighter it can be wound around the disc, making more space.
