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1.1 Components of a computer and their uses Flashcards

1
Q

1.1.1 (a) CU

A

Control Unit
Coordinates all activities of the CPU (Communicates with all parts of the CPU)
Directs the flow of data between the CPU and other devices
Accepts the next instruction, decodes and handles execution and stores the data in memory or registers
Sends memory read/write requests to main memory on the control bus: As well as other command/control signals
Bus and interrupts requests/grants
Uses the SRs and the Clock

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2
Q

1.1.1 (a) PC

A

Program Counter: Register
Holds the address of the next instruction to be executed (in a sequence of instructions)
Increments after each instruction in a sequence
Holds the address to jump to if there is a branch or jump command
Linked with the MAR: Data is copied from the PC into the MAR

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3
Q

1.1.1 (a) MAR

A

Memory Address Register
Hold the address of the memory location w=from which data/instructions are to be fetched from/written to
Uses the address bus

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4
Q

1.1.1 (a) MDR/MBR

A

Memory Data/Buffer Register
Temporarily Stores Data which is read from/ written to memory
All data to/ from memory passes through the data bus and MDR

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5
Q

1.1.1 (a) CIR

A

Current Instruction Register
Holds the current instruction being executed
Contents of the MDR are copied into the CIR (If the MRD contains an instruction)
Contains the Opcode and the Operand

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6
Q

1.1.1 (a) ALU

A

Arithmetic Logic Unit
Preforms Arithmetic and Logical Operations on Data
Operations of Numbers: ADD, SUBTRACT, MULTIPLY, DIVIDE
Also preforms Bitwise Shifts
Boolean Logic: Comparison, AND, OR, NOT, XOR
Makes use of General Purpose Registers to Store Results

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7
Q

1.1.1 (a) ACC

A

Accumulator: Register
Special Case of General Purpose Register
Stores data/ control information
Linked with the ALU

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8
Q

1.1.1 (a) Buses

A

Address Bus: Carries memory addresses that correspond to read/write locations in memory (1 directional)
Data Bus: Carries actual information being transmitted around the computer (2 directional)
Control Bus: Carries command and control signals to/from all components, e.g. Read/Write Signals

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9
Q

1.1.1 (b) Fetch

A

The programs counter is checked as it holds the next address
The address is copied into the MAR
The address is sent along the address bus to main memory, where is waits to receive a control signal.
The CU sends a control signal
MDR takes the result via the data bus and copies it into the CIR
The PC increments

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10
Q

1.1.1 (b) Decode

A

Preformed by the CU
The data in the CIR is split into the
Opcode: What to do
Operand: What to do it to (address or data)
The CU prepares for the execution stage

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11
Q

1.1.1 (b) Execute

A

The process is carried out
The process repeats

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12
Q

1.1.1 (b) Branching

A

If the operand contains a branch, the operand (address to branch to) is copied into the PC

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13
Q

1.1.1 (c) Clock Speed

A

Measured in Hertz (Hz) number cycles of instructions executed per second
Higher clock speed = Higher performance
Modern Computers use Gigahertz (GHZ) Billions of Cycles per Second

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14
Q

1.1.1 (c) Cache Size

A

Temporary storage of data and instructions
Being read from/ written to
Stores copies of recent data and instructions
Faster
Limited due to Cost

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15
Q

1.1.1 (c) Number of Cores

A

Multiple cores can run multiple programs at the same time
Cores communicate, which takes time
The software needs to be able to make use of multicore systems for improved performance

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16
Q

1.1.1 (d) Pipelining

A

Multiple Instructions are overlapped, to further improve CPU performance.
Different parts of the FDE cycle happen to different instructions simultaneously
Registers are more efficient, as different instructions can be processed at the same time

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17
Q

1.1.1 (d) Instruction Pipeline

A

The stages that an instruction moves through the processor

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18
Q

1.1.1 (d) Arithmetic Pipeline

A

Parts of an arithmetic operation that can be broken down and overlapped

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19
Q

1.1.1 (d) Flushing the Pipe

A

When branching and jumps are occur, the pipeline must be flushed, as lines which are being fetched / decoded are not need, so they must be removed.
Limits benefits of pipelining with a program with lots of branching

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20
Q

1.1.1 (e) Von Neumann Architecture

A

Shared memory space for data and instructions
Instructions and data are stored in the same format
Single CU/ Processor
Follows a linear FDE cycle
One instruction is processed at a time
Registers are used as fast access to instructions and data

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21
Q

1.1.1 (e) Harvard Architecture

A

Instructions and data are stored in separate memory units
Instructions and data use separate buses
Reading/ Writing data can be done at the same time as fetching instructions
Used by RISC computers

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22
Q

1.1.1 (e) SIMD

A

Contemporary Architecture
Single Instruction Multiple Data
Parallel Processing carries out a single instruction on multiple data items at the same time
Used in Graphics Processors

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23
Q

1.1.1 (e) MIMD

A

Contemporary Architecture
Multiple Instructions Multiple Data
Multiple Instructions are carried out across several cores

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24
Q

1.1.1 (e) Distributed Computing

A

Contemporary Architecture
Multiple Computers on a shared network sharing resources to tackle a larger problem

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25
1.1.2 (a) Instruction Set
A set of all instructions in machine code that can be executed by a given processing unit or CPU
26
1.1.2 (a) CISC
Complex Instruction Set Computer Aims to complete tasks in as few assembly lines as possible Processor hardware and circuitry is more complex to understand and execute a series of operations Commands resemble high level language Instructions may take multiple clock cycles to execute Many Instructions of Variable Length Multiple Addressing modes available
27
1.1.2 (a) CISC Pros and Cons
Pros: Efficient Use of RAM Small Code sizes Cons: More Expensive Cannot Pipeline Processor hardware and circuitry is more complex to understand and execute a series of operations
28
1.1.2 (a) RISC
Reduced Instruction Set Computer Simple Instructions Instructions take one clock cycle to complete Compiler has more work to translate Less Complex Hardware Fewer addressing modes
29
1.1.2 (a) RISC Pros and Cons
Cheaper Pipelining possible same execution length Lower energy requirements Cons: More RAM used Takes more code lines in assembly
30
1.1.2 (b) Co-Processor Systems
Any additional processor used for a specialised task Improve Computing speed by executing concurrently with the main CPU
31
1.1.2 (b) GPU
Graphical Processing Unit Used to render graphics Many cores: Processes many parallel streams of data at the same time Highly specialised: More Efficient/ Faster at executing Simple operations on larger data sets Uses SIMD which can be used across any data set
32
1.1.2 (b) GPGPU
General Purpose Graphical Processing Unit Used to carry out one instruction over multiple data items
33
1.1.2 (b) GPU and CPU differences
GPU: Executing simple operations on larger data sets CPU: Executing complex instructions on smaller data sets
34
1.1.2 (b) Uses of GPUs
Rendering Graphics Machine Learning Statistical Analysis Weather Modelling Oil Exploitation Stock Option Predictions Gravitational Field Theory
35
1.1.2 (c) Methods of coping with the demand for CPU performance
Co-Processor Multicore Systems Parallel Processing
36
1.1.2 (c) Multicore Systems
A single physical chip containing two or more independent processing units Each core preforms it's own FDE cycles Cores are on a chip multiprocessor (CMP)
37
1.1.2 (c) Improving Performance / Limits of Multicore Systems
On chip shared cache Inter core communication Limits: Overhead with Inter core communication Some programs cannot make full use of all cores
38
1.1.2 (c) Parallel Processing
The processing of program instructions by dividing them between multiple processors, or processor cores. Each stage of the FDE cycle can be carried out by individual processing units Performance depends on the task and program
39
1.1.3 (a) Input Device
Any device that allows you to pass information from the outside world into a computer system
40
1.1.3 (a) Output Device
Any device that takes data stored in digital form and converts it into another format that humans can process such as sound, images or vibrations
41
1.1.3 (a) Storage Device
Any device used for either temporary or permanent storage of data, internally or externally
42
1.1.3 (a) Input Devices Examples
Mouse Keyboard Microphone Barcode Scanner Webcam Magnetic Stripe Reader Chip and Pin Optical Character Recognition
43
1.1.3 (a) Output Devices Examples
Visual display unit Printer Projector Headphones Speakers Digital Projector Plotter Actuator Touchscreen
44
1.1.3 (a) Storage Devices Examples
Internal: Main Memory (RAM) Solid State/ Hard Drives External: Optical disk USB pen Memory card External hard disk drive Cloud
45
1.1.3 (b) Drive and Media
Drive: The device that reads and writes data from secondary storage Media: What the data is stored on
46
1.1.3 (b) Optical Storage Media
CD: Compact Disk DVD: Digital Versatile Disk Blu-Ray R: Read Only RW: Read/Write
47
1.1.3 (b) Optical Storage Uses
CD-R: Music DVD-R: Motion Picture CDR-W: Backups DVD-RW: Greater Storage Backups Blue-Ray: An alternative, supersedes DVD in capacity
48
1.1.3 (b) How Does Optical Storage Work
A Laser is shone onto media, the reflection is processed Light scatters based on how reflective a material is During creation, a laser burns the disk creating pits and lands (Read only) Chemical Composition is changed by a reversible chemical reaction (Read and Write Only) Data is read from the inside to the outside
49
1.1.3 (b) Pros and Cons of Optical Storage
Pros: Cheap Lightweight Portable DVDs can store more due to higher precision lasers Cons: Slow access times Prone to scratches
50
1.1.3 (b) Magnetic Disks Media
Magnetic Hard Disk Drives Magnetic Tapes
51
1.1.3 (b) How does Magnetic Media Work
North and South Polarity Magnets Many magnetised compounds are stored in the same space Drive Head moves over the disks
52
1.1.3 (b) Magnetic Disks Pros and Cons
High Capacity Slower as it contains moving parts Mechanical Components will fail eventually
53
1.1.3 (b) Magnetic Tapes Pros
High Capacity Used for Backups Cheap Portable Sequential Read / Writes Slow Fragile
54
1.1.3 (b) How does Solid State / Flash Media work
A flow of electricity forces electrons into a floating gate between two oxide layers, causing a change in charge which can be measured
55
1.1.3 (b) Solid State / Flash Media Pros and Cons
Small Lightweight Silent Fast Access Durable Oxide Layer deteriorates, causing a limited life span of Read/Writes Costly
56
1.1.3 (b) Solid State / Flash Media Types
Solid State Drive Memory Sticks Flash Memory Cards
57
1.1.3 (c) ROM
Read-Only Memory Small Piece of memory located on the motherboard Non-Volatile Contains the very first instructions for the computer (bootstrap) The Bootstrap preforms the hardware checks and Loads the Bios Responsible for the Power On Self Test (POST): Wakes up and links components Contains Firmware
58
1.1.3 (c) RAM
Random Access Memory Temporary Storage of Data and Instructions Holds Information being executed by the processor Volatile Faster than the Hard Disk: Data is moved from the hard disk to RAM Stores the operating system whilst the computer is running
59
1.1.3 (d) Virtual Storage
Cloud Storage The concept of storing and retrieving data over the internet in the cloud instead of a local storage device
60
1.1.3 (d) Pros of Cloud Storage
Data is accessed any time on any device with an internet connection Data can be easily shared (Collaboration) Scalable (Lots of Available Storage)
61
1.1.3 (d) Cons of Cloud Storage
Expensive Requires an internet connection Requires a good internet connection for fast access times Storage in permanent locations
62
1.1.3 (d) Alternative Interpretation of Virtual Storage
The abstraction of logical storage from physical storage A single drive with files may be spread across different media types Storage area appears neatly organised to the user The data is actually stored in many physical locations

Computer Science (4 decks)

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