Systems architecture, memory, storage Flashcards
Explain the Fetch Decode Execute cycle
-Fetch an Instruction from main memory
-Decode the instruction
-Execute the instruction
What is cache memory
Cache memory is very fast memory used to temporarily hold data or instructions that are likely to be used again by the processor in the course of running a program
In Von Neumann architecture are the data and instructions stored in the same memory
Yes
What does the Control Unit do?
The CU coordinates all the activity within the CPU. It can:
-control the execution of instructions in the correct sequence
-decode instructions
-send and receive control signals to and from devices within the computer
What does the Arithmetic and Logic Unit to?
The ALU carries out the following functions:
-Logical Operations
-Binary shifts
-Arithmetic operations
Name 4 registers inside the CPU
-Memory Address Register
-Memory Data Register
-Program Counter
-Accumulator
What is a special purpose register
A register is a very fast memory location within the CPU, used within the CPU for the execution of instructions
What does the MAR stand for and do?
Memory address register, holds the address (location in memory) of the instruction or piece of data to be fetched or stored
What does the MDR stand for and do?
Memory data register, holds data or a program instruction temporarily when it is fetched from memory or is to be sent to memory
What does the PC stand for and do>
Program Counter; holds the memory address of the next instruction to be processed
What does the ACC stand for and do?
The accumulator is a special-purpose, memory location where the results of operations carried out in the ALU are temporarily stored
What are the 3 main factors affecting CPU performance?
-Clock speed
-Cache size
-Number of cores
What is the clock speed?
the number of instructions a single processor core can carry out per second
What is cache memory?
stores regularly used data for quick access.
-it is low capacity
-it is expensive
The _____ cache memory a computer has the ______ the performance
more, better
How does the number of cores affect speed. What is a core
Each core processes data independently, meaning more instructions can be carried out per second with more cores.
Which type of memory is most expensive?
Cache memory
What is an embedded system?
computer built into another device. e.g. washing machine, microwave
Name 3 advantages of embedded systems
-Easier to design
-Cheaper to produce
-More efficient at tasks
Name an off-line storage device that is read-only and cannot be written to
ROM
What type of memory is used as the computer’s main memory?
RAM
What is hardware?
physical parts of a computer
What is software?
programs that a computer system runs
Why is virtual memory used?
When there isn’t enough main memory to store the entirety of a program so some data is moved to a location in secondary storage.
-THis data is moved back to RAM when the CPU needs it.
-Data transfer is slower on secondary storage, so this slows the computer’s performance.
Name some non-volatile storage forms
HDD, SDD, ROM
Name a volatile storage form
RAM
List the 4 features of ROM, and what it is
ROM (Read Only Memory) is the main permanent memory in a computer. It is:
>non-volatile
>read-only
>small amount of memory build into the motherboard
>Contains BIOS (Basic Input Output System)- instructions for the pc to boot up
List 4 features of RAM, and what it is
RAM (Random Access Memory) is the main temporary memory in a computer. It is;
>Volatile
>Can be read and written to
>Programs and files are copied here from secondary storage while in use
>Slower than CPU cache but faster than secondary storage
Define PRimary storage
memory that the CPU can read/write to quickly, e.g. RAM
Define Volatile
Storage / memory where data is lost when power is removed.
Define Non-Volatile
Storage/Memory where component retains data even when power is turned off
Name 2 types of internal storage
-Hard Disk Drive (HDD)
-SDD (Solid State Drive)
Name 3 characteristics of HDDs
-Moving Parts
-Store data magnetically on metal disks
-Can be noisy
Name 3 characteristics of SDDs
-No moving parts
-Use flash memory for faster read/ write times
-Usually silent/ quiet
Name 4 types of external storage
-Flash drives/ memory cards
-Optical disks
-Magnetic tape
-External HDDs & SDDs
When are flash drives and memory cards used?
solid state storage used to expand the capacity of small devices
Name 3 optical storage types
-CDs
-DVDs
-Blu-ray
What is the definition of optical storage
Makes use of a laser to shine and reflect light to read the data stored
What are 3 properties of optical storage
-Low capacity compared to other types of storage
-SLow to access data
-Thin, lightweight, portable
Name 3 Solid state storage devices
-SSD
-Memory Sticks
-Flash memory cards
Name 4 characteristics of solid state storage
-High storage capacity
-quick access to data
-no moving parts so high reliability
-no noise
-low power
-no need to defragment
Define solid state storage
Use non-volatile random access memory to store data indefinitely
Name 2 magnetic storage types
-Hard Disk Drives
-Tape
Name 4 characteristics of magnetic storage
-High storage capacity
-QUick access to data
-Has a moving part which eventually fail
-hard disks perform better if they are defragmented
Define magnetic storage
Makes use of a magnetisable coating. Magnetised dots are made on the surface of the material, these dots are created, read, and erased by very small electromagnets.
What are the bumps and grooves on a DVD or CD called?
pits and lands
I want to make a backup of 125 photos, which each take up 16MB of disk space. What is the minimum amount of secondary storage space that I need?
equation for required capacity:
RC = number of files x size of single file
substitute values.
RC = 125 x 16MB = 2000MB
MB –> GB
NUmber of MB/1000 = GB
convert to appropriate units:
2000MB/1000 = 2GB
Describe the fetch stage
Fetch the next instruction from main memory(RAM)
-Bring back to CPU
Describe the decode stage
-Inspect the instruction and work out what it is that needs doing
Describe the execute stage
-Carry our the instruction
-Could include activities such as
-going back to main memory and fetching data
-performing a calculation
-storing information back into main memory
What does the control unit do?
Controls the flow of data in and out of the CPU, manages the FDE cycles
What happens at the Fetch stage?
-Memory address copied from PC to MAR
-Instruction copied from memory to MDR
-PC incremented to point to the next instruction
What happens at the Execute stage?
-Decoded instruction carried out.
Example instructions:
-Load data from memory
-write data to memory
-do calaculation of logicoperation
WHat happens at the Decode stage?
-Instruction in the MDR decoded by CU
-CU prepares for the next step, e.g. loading values into the MAR or MDR
Does the FDE cycle ever end?
The fetch-execute cycle runs continuously while the computer is running
What holds the address of the next instruction to be executed
MAR
Data stored here is not erasable and usually contains instructions for booting the system, what am I?
ROM
Arithmetic and Logical instructions are carried out here:
ALU
