System Architecture Flashcards
What is the purpose of the CPU?
The CPU carries out processing on the computer, it does this by fetching and executing instructions
Describe the processes involved in the Fetch-decode-execute cycle.
The Processor fetches the next instruction to be executed from memory.
The address of the next instruction is stored in the Program Counter.
The current instructions address is stored in the MAR.
The Program counter is incremented.
The instruction is stored in the MDR.
The instruction is decoded.
The instruction is executed.
And the cycle begins again.
What is the function of the ALU?
Arithmetic logic unit
carries out mathematical and logical operations including AND, OR and NOT, and binary shifts
What is the function of the CU?
Control Unit
Coordinates all of the CPU’s actions in the fetch-decode-execute cycle
What is the function of the cache?
Sends and receives control signals to and from other devices within the computer
What is the function of registers?
They are smaller and faster than cache
Registers are memory locations within the CPU to temporarily store memory addresses, instructions and data
Who developed the Von Neumann architecture?
John Von Neumann
What is the Von Neumann architecture also known as?
the stored program computer
What is the Von Neumann Architecture?
In a Von Neumann computer, both programs and the data they use are stored in memory
What is the function of the MDR?
Memory Data Register
holds data or program instruction when it is fetched from memory or data that is waiting to be written to memory
What is the function of the accumulator?
its a register in which the results of the operations carried out in the ALU are stored
What is the function of the PC?
Program Counter
holds the memory address of the next instruction to be processed
What is the function of the MAR?
holds the address (location in memory) of the current instruction or piece of data to be fetched or stored
What is the purpose of the clock speed?
It determines the number of fetch-decode-execute cycles per second, as every action in the CPU takes place on a clock cycle.
Why is cache memory used?
Cache memory operates much faster than main memory, data is transferred in and out of cache memory more quickly, which makes the CPU more efficient as less time is spent waiting for data to be transferred.
What is an embedded system?
It is a microprocessor that is designed to perform a dedicated function within a larger computing system. It includes RAM, ROM and a CPU.
Why must embedded systems be reliable?
The user cannot change the software held in ROM within the embedded system (cannot be changed once manufactured)
What are some examples of embedded systems?
washing machines, digital cameras, satnavs, radio alarm clocks
What is the purpose of cores?
Each core can process one operation per clock cycle.
Explain why a computer with a dual or quad core may not be twice as fast as a single core processor with the same clock speed?
Additional cores may be redundant if the software is only written for one core or if the output of one operation is required to perform the second operation
What is another name for main memory?
RAM (Random Access Memory)
What is the purpose of RAM?
It temporarily stores the programs, instructions and data the computer needs whilst in operation
Why is data copied from the hard disk into main memory?
Because it would be much slower to access everything directly from the hard disk
What are the pros and cons of RAM?
➜ it’s volatile (all data is lost when the power is turned off)
➜ used for the computer’s working memory for instructions, programs and data
➜ can be written to and read from
What are the pros and cons of ROM?
Read-only memory
➜ non-volatile (data is permanently retained without power)
➜ used for the computer’s start-up instructions and in embedded systems
➜ Read only, so cannot be written to
Explain why increasing ROM size would not improve performance.
Any additional space will make no difference.
New files cannot be written into new space as it is read-only.
When is virtual memory used?
Virtual memory is used when there simply isn’t enough space in RAM for all of the programs and data you are currently working on
What is virtual memory?
When a small section of the hard disk is reserved to act like RAM. When the program in virtual memory is needed, it is swapped with something else in RAM
Why might swapping between virtual memory and RAM cause your computer to slow down?
since access to the hard disk isn’t nearly as fast as RAM and it can cause disk thrashing, which decreases performance
What are some examples of secondary storage?
➜hard disk (internal and external)
➜USB flash drive
➜CDs
What is the purpose of secondary storage?
We need it for longer term storage of files and data because it is non-volatile.
External devices are portable and may have very large capacities.
What are the pros and cons of SSDs?
Solid State Drive
➜durable and reliable (due to no moving parts)
➜thin so can be used in small portable devices (due to no moving parts)
➜create little heat and don’t require expensive cooling equipment
➜efficient power consumption
➜high capacity
➜can be expensive
What are the pros and cons of HDDs?
Hard Disk Drives ➜High capacity ➜Inexpensive compared to SSDs ➜Fast and durable ➜Can be affected by magnetic fields and heat ➜Contain moving parts ➜Require expensive cooling systems
What are the pros and cons of optical storage devices?
➜Portable ➜Have a life expectancy of 10-25 years ➜Lightweight ➜Susceptible to scratches ➜Will degrade over time with exposure to sunlight ➜Cheap
What are some examples of SSDs?
➜Flash USB Memory stick
➜Memory cards
What are some examples of optical storage devices?
➜CDs
➜DVDs
➜Blu-Ray
What are the components in a HDD?
➜Drive read/write head
➜Drive spindle
➜Magnetic platter
What is the purpose of the drive read/write head?
It moves into position to either read data from or write data to, the disk- this movement takes additional time.
What is the purpose of the drive spindle?
It rotates the disk
Moving parts can cause issues if dropped
What is the purpose of the magnetic platter?
➜It stores data.
➜It can be affected by heat and magnetic fields.
➜Multiple players provide a large storage volume
