Hardware and Communication Flashcards
Components in CPU architecture
CIR
* Register that holds the instruction currently being executed.
Registers
* A small amount of fast access storage
Control Unit
* Directs the flow of instructions and data
* Coordinates the parts of the CPU
* Generates clock ticks
* Decodes instruction
* Handles execution
Arithmetic Logic Unit
* The ALU performs all the mathematical calculations and logical operations in the CPU.
MDR
* Register of a computer’s control unit that contains the data to be stored in the computer storage, or the data after a fetch from the computer storage.
MAR
* MAR holds the memory location of data that needs to be accessed.
PC
* Holds memory address of instruction for each cycle
Buses
* Connects all the internal components of a computer, such as CPU and memory, to the motherboard.
Cache memory
* stores copies of the data from frequently used main memory locations.
* Cache is usually organized as a hierarchy of more cache levels (L1, L2, etc.)
Internet
Internet
- Network of networks
Characteristics of HDD
- Hard drives have a fast transfer rate and a fairly fast access time.
- Hard drives are a magnetic medium and store data on a hard drive platter
- Data is read and saved using an arm that has a special read/write head at the end
- As the disk spins, the arm travels across the disk
- Each sector of the platter can store data and the movement of both the disk and the read/write head means that every sector on the hard drive can be reached
- The faster the platter spins, the faster data can be read from the disk.
SSD fragmentation
SSD fragmentation
* An SSD drive uses direct access to data
* There would be no deterioration in read times
* as there is no physical read-head to move
Protocols
DHCP (Dynamic Host Configuration Protocol) - Assigns dynamic IP addresses to devices on a network. This is important as the DHCP protocol ensures that unique/dynamic IP addresses are allocated / allows addresses no longer in use to be automatically returned to the pool of available IP addresses for reallocation
SMTP - allows emails to be sent over a network. This is important as the SMTP provides a standard way of transferring emails between two different servers.
HTTP - Transfers webpages over a network. This is important as the HTTP protocol allows multiple different web browsers to display and format web pages as the original author intended
UDP - (Universal Datagram Protocol)
sends datagrams across a network with very few error recovery services. This is
important as, for example, video and audio streaming protocols are designed to handle occasional lost packets and need to receive new packets rather than the retransmission of previous ones
FTP (File transfer protocol) - allows the transfer of large files over a network. This is important as the FTP protocol has in-built error checking and re-transmission request as necessary
Internet Message Access Protocol (IMAP) - allows emails to be transferred between computer systems (via the internet). This is important as the IMAP provides a standard way of transferring emails between two different servers / messages are stored on the server instead of mobile devices, which saves storage space
Transmission Control Protocol (TCP) - allows any networked computers to
communicate with each other. This is important as TCP/IP specifies how signals are routed and transported around a network (and reduces the need for gateways to convert signals into different protocols)
IP (Internet Protocol) - Delivers data packets
Parallel Processing
Parallel Processing
- Parallel processing is a form of computation in which many calculations are carried out simultaneously
- Parallel processing uses multiple cores
- It operates on the principle that large problems can often be divided into smaller ones, which are then solved concurrently
- Parallel processing in computer programs is more complex to design and to write than sequential computer programs
- Communication and synchronisation between the different subtasks are typically some of the greatest obstacles to getting efficient parallel program performance
- Multiple processors are used
- Many calculations are carried out simultaneously / at the same time
- Large problems can be divided into smaller ones,(which are then solved concurrently).
- Parallel computer programs are more complex to design and to write than sequential ones
- Concurrency introduces several new classes of potential software bugs
- Race conditions are the most common class of potential software bug
- Communication and synchronisation between the different subtasks creates an overhead. Accept a suitable example of this.
Cache
Cache
- is similar to RAM, except it resides on or close to the CPU
- is faster than RAM and is also volatile
- used to store frequently used data from main memory
- used by the processor to avoid having to slow down to the speed of the RAM all the time
- used to store intermediate results to calculations
- Different levels of cache memory which denote speed and characteristics
- Von Neumann bottleneck solution
- Cache memory is typically integrated directly with the CPU.
- Cache memory can also be placed on a separate chip / located between the CPU and RAM (that has a separate bus to connect with the CPU).
- Cache memory stores program instructions that are frequently re-referenced by software during operation*.
- As a CPU processes data, it looks in the cache memory first to see if the instructions are there from a previous reading of data.
- Cache memory is expensive compared to conventional RAM.
- Cache memory is smaller than RAM.
- Cache memory is categorised as “levels” that describe its closeness and accessibility to the CPU.
- Least used data / instructions are overwritten when cache is full.
Advantage
- Cache memory is memory that a CPU can access more quickly than it can access regular RAM.
- Cache memory ensures fast access to these instructions which increases the overall speed of the software program.
- Computers with slower processors but larger caches tend to be faster than computers with faster processors but more limited cache space.
SSD
SSD
- Solid State Drives feature a non-mechanical design of NAND flash mounted
on circuit boards
- NAND flash is shock resistant
- SSDs have faster data access than BD
- No moving parts to an SSD
- Files are stored on microchips
- Non-volatile.
SSDs are more durable:
- Solid State Drives feature a non-mechanical design of NAND flash mounted on circuit boards
- NAND flash is shock resistant
- Traditional HDD consist of various moving parts making them susceptible to shock and damage.
SSDs are faster:
- SSDs have greater performance
- SSDs have faster data access
- Computers with SSDs have quicker boot up time
- HDDs can only access the data faster the closer it is from the read write heads, while all parts of the SSD can be accessed equally.
SSDs do not require defragmentation
- Defragmentation may perform “trim” command which may slightly improve the speed of future write operations
SSDs consume less power:
- SSDs use significantly less power at peak load than hard drives
- SSDs energy efficiency can deliver longer battery life in laptops.
SSDs are lighter / smaller:
- Flash-based SSDs weigh considerably less than hard drives.
- Increased portability
SSDs are cost-efficient (NOT cheaper):
- SSDs offer cost savings in the long run for businesses with lower energy usage and greater productivity.
SSDs run cooler:
- SSDs require very little power to operate which translates into less heat output by
the system.
SSDs are quieter:
- With no moving parts, SSDs run at near silent operation
Blue-ray Drive
Blue-ray drive
- Optical drives work by using lasers to store data
- Burning microscopic indentations into a disc
- This pattern of indentations is created in a spiral pattern, starting from the middle
- Indentations and their absence create pits and lands
- A laser is aimed at the disc and reflected back, which can cause interference with the original laser
- Blu-ray data is stored on two layers
- Blu-ray data can be stored on both sides of the disc
- Two lasers of differing wavelength are used to read data from the two layers
- Pits and lands are stored closer together, meaning that the laser’s wavelength must be shorter (blue)
- Non-volatile (retains data)
Fragmented
Fragmented files are split up and stored on different parts (tracks) of the disc
It can take longer to access a fragmented file because there is more read/write head
movement to locate all the file parts and this movement (with damping) takes time.
When a hard disc is defragmented parts of files are physically moved closer together to reduce read/write head movement.
Fetch-Decode-Execute
Fetch:
- The address of the next instruction is copied from RAM into the register (PC to the MAR)
- The instruction (at that address) is copied to the MDR
- The PC is incremented (so that it holds the address of the next instruction)
Decode:
- The MDR is copied into the Current Instruction Register (CIR)
- The instruction / data (opcode / operand) is decoded
Execute
- The instruction is carried out.
- Each stage is designed to happen concurrently to maximise resources use
Lossy Compression
Lossy Compression
- Data compression reduces the file size
- When compressed files are decompressed they do not give back the original data
- Because lossy compression cannot be decompressed to yield the exact original data, it is not a good method of compression for critical data, such as textual data
- It is most useful for digitally sampled analogue data, such as sound, video, graphics or images
- Some examples of lossy data compression algorithms are JPEG, MPEG, and MP3.
- Algorithms for lossy compression vary, but many use a threshold level truncation. /suitable lossy data compression example
Protocol
A protocol is an agreed set of rules which allows two devices to communicate the transfer of data
Role of handshaking - When a computer system establishes a devices readiness to communicate. speed of transmission, error correction, and character set to be used are agreed.
RAM
RAM
- stores programs that are currently being executed
- RAM is volatile (contents lost when power is lost)
ROM
ROM
- cannot be changed or deleted
- non-volatile (retains data)
- stores bootstrap program, needed to start the program and any system data that does not need to be changed
