1.1 Processors Flashcards
What is the accumulator?
A special register to temporarily store the results of operations performed by the ALU
What is the address Bus?
Carries the memory location addresses to be read from or written to (cpu to ram)
What is the arithmetic logic unit?
A part of the CPU that performs arithmetic calculations and logical operations on data for the computer programs
Buses
A physical set of parallel wires connecting and carrying groups of bits between several components of a computer
What is cache?
A small and fast but expensive memory in the CPU used to store instructions and data that are accessed regularly
Clock speed
The frequency at which the internal clock generates signals switching between 0 and 1. It controls how often instructions are executed and data is fetched
Contemporary architecture
A modern architecture combining Von Neumann and Harvard architectures
What is the control bus?
A bi-directional bus carrying control signals from the CU to synchronise access and use of data
What is the Control Unit
A part of the CPU that controls and manages the execution of instructions. It sends control signals to coordinate execution and controls FDE cycles and buses.
What is the Current instruction register?
A special register that stores the current instruction being executed and decoded. These instructions and divided into operand and opcode.
What is the data bus?
A bi-directional bus for carrying data and instructions between the processor and memory
FDE cycles
Fetching from memory, decoding and executing the instruction
What is fetching
Supplying the address and retrieving the instruction from memory
Harvard architecture
A computer architecture that stores data and instructions in separate memories to allow the next instruction to be read whilst data is currently being read or written
Memory address register
A special register that stores the memory address of the next instruction to load or data to use
Memory data register
A special register that temporarily stores data to be read from or written to in main memory
Number of cores
A core is a processing unit that handles instructions with its own FDE cycles. Multi-core processors have multiple cores that can run simultaneously
Pipelining
The simultaneous decoding of several instructions by decoding the next instruction and fetching the one after while the current one is being executed
Program counter
A special purpose register that stores the address of the next instruction to execute
Registers
Special memory cells that can be accessed quickly. They temporarily store data and control information
Von Neumann architecture
Architecture where a single control unit manages program control via a linear sequence of FDE cycles
Complex instruction set computer (CISC)
A more complicated and expensive processor design that can execute a series of tasks in a single complex instruction built into the hardware. The variety of instructions means less RAM is used.
What cannot be used with a complex instruction set computer?
Pipelining
What is a Graphic processing unit?
A specialised processing unit with a huge number of small cores that allow efficient parallel computation for tasks such as computer graphics, machine learning, data mining
Multicore systems
Several CPU cores are incorporated into a single processor chip to help distribute wotkload
Parallel processing system
Splitting a job into several subtasks which are simultaneously carried out by each core in the system
Reduced instruction set computer (RISC)
A simpler processor design that can only execute a single simple instruction each clock cycle. This used more RAM but allows pipelining.
Flash storage
A solid state technology that stores data on a collection of memory chips, no moving parts as data is accessed by software
Input devices
Peripheral devices that allow the user to communicate and to pass readable data into a computer, decode it and send it to the CPU
Magnetic storage
Relies on the polarisation of magnetic particles to store bits on a magnetic material which is typically moved mechanically. A high capacity and low cost means of storage
Optical storage
Data is stored in the reflectivity (pits and lands) of a surface, and is read and written to by a laser
Output devices
Peripheral devices that take and convert signals from a computer into a human-readable form
Random access memory
Memory used to store programs and data in use by the computer, Quick access times by al data is lost when the computer is turned off (volatile)
Read only memory
Memory used to store information that is permanently required to boot up and run the computer. Cannot be written to and is non-volatile.
Storage device
Any medium on which data can be stored even when powered off
Virtual storage
Using the hard disk as though it were an extension of memory to free up more RAM for current programs
Name 3 jobs the control unit performs
- Controlling and coordinating the activities of the CPU
- Managing the flow of data between the CPU and other devices
- Accepting the next instruction
- Decoding instructions
- Storing the resulting data back in memory
Name three control signals sent by the control bus
- Bus request: shows that a device is requesting the use of the data bus
- Bus grant: shows that the CPU has granted access to the data bus
- Memory write: data is written into the addressed location using this bus
- Memory read: data is read from a specific location to be placed onto the data bus,
- Interrupt request: shows that a device is requesting access to the CPU
- Clock: used to synchronise operations
What is assembly code
uses mnemonics to represent instructions. Simplified way of representing machine code
In assembly what is the instruction divided into
Operand and opcode (happens in the CIR)
What does the operand contain?
Data or the address of the data upon which the operation is to be performedWh
What does the opcode specify?
Type of instruction to be executed
How many separate FDE cycles need to be running simultaneously for pipelining?
3
Where is appropriate data held in pipelining?
A bugger in close proximity to the CPU until is required (one fethced, one decoded and one executed)
What is pipelining aimed to reduce?
The amount of the CPU which is kept idle
What is pipelining separated into?
Instruction pipelining and arithmetic pipelining
What is instruction pipelining?
Seperating out the instruction into fetching, decoding and executing
What is arithmetic pipelining?
Breaking down the arithmetic operations and overlapping them as they are performed.
What happens in the fetch phase?
- Address from the PC is copied to the MAR
- Instruction held at that address is copied to MDR by the data bus
- Simultaneously, the contents of the PC are increased by 1
- The value held in the MDR is copied to the CIR
What happens in the decode phase?
The contents of CIR are split into operand and opcode
What happens in the execute phase?
The decoded instruction is executed
What is clock speed determined by and what is it
System clock which is an electronic device which generates signals, switching them between 0 and 1. all processor activities begin on a pulse. Time taken for one cycle to complete
What is a core?
An independent processor that is able to run its own fetch-decode execute cycle.
What happens as cache fills up
Unused instructions are replaced
What concept is the Von Neumann architecture built on?
Stores program concept
What is Harvard architecture commonly used with?
Embedded processors
What does Harvard architecture do with memories?
Physically separates memories for instructions and data
Why is Harvard architecture useful when memories have different characteristics?
instructions may be read only, while data may be read-write.
This also allows you to optimise the size of individual memory cells and their buses
depending on your needs, i.e. the instruction memory can be designed to be larger so a
larger word size can be used for instructions.
Advantages of Von Neumann architecture?
Cheaper to develop as the control unit is
easier to design
Programs can be optimised in size
Advantages of Harvard Architecture?
Quicker execution as data and instructions
can be fetched in parallel
Memories can be different sizes, which can
make more efficient use of space
When is Von Neumann architecture used in contemporary processing?
when working with data and instructions in main memory
When is Harvard architecture used in contemporary processing?
to divide the cache into instruction cache and data cache
Where are complex instruction set computers used
Microcontrollers and embedded systems
RISC processors and use of RAM
More RAM required
CISC processors and use of RAM
Less RAM is required since code is shorter
Why is pipelining possible with RISC
Each instruction takes one clock cycle
What happens with CISC and specialised instruction?
Many specialised instructions are made,
even though only a few of them are used
How do parallel systems still only requite one core?
They use threading
What systems perform best in larger projects (multicore or parallel)?
Multi-core systems
How do GPU’s work
Use lots of independent processors which work in parallel making it efficient for repetitive tasks
What are some repetitive tasts that GPU’s are good at
Image processing and machine learning
What is a co-processor?
a secondary processor designed to supplement the activities of the primary processor
Example of a type of co-processor
GPU’s
What is a magnetic stripe reader?
Used to read data from magnetic stripes on cards like credit and debit cards
What is a barcode reader?
Used in supermarket checkouts and access control systems to read information
from printed labels and cards
What is a webcam?
A camera used by a computer to take photos and record videos
What is a keyboard?
Used to enter text into a computer
What is a speaker?
Used to output sound from a computer
What is a printer?
Used to output information from a computer onto paper
What is a projector?
Used to project video content from a computer onto a screen
Example of a device that is both input and output
Monitor with touch input
How is data written with a laser on optical storage
Through spiral tracks that contain pits and lands which either reflect or scatter the incident laser
What do pits represent?
0
What do lands represent?
1
Disadvantages of CD’s
easily damaged by scratches, their limited
storage capacity and relatively slow transfer speeds
What does CD stand for?
Compact disc
What does DVD stand for?
digital versatile disc or digital video disc
Difference between DVD and CD?
DVD’s have a higher storage capacity than CDs
Difference between Blu-Ray and DVD’s?
blu-ray discs have more than five times as much
storage than traditional DVDs, making them useful for storing high-resolution films
Two states of magnetic storage
Polarised and unpolarised
Polarised on a magnetic disk?
If a portion of magnetic material is polarised,
all magnetic poles align and can be read by a read/write head passing over the region
Unpolarised on a magnetic disk?
If an area is not polarised, magnetic poles are randomly scattered and produce a different
reading on a read/write head
Give 3 types of magnetic storage
Hard disk drives, magnetic tape and floppy disks
How do hard drives work?
They work by rotating magnetic platters at high speeds
under a read/write head on an actuating arm. The combination of the arm and
rotating platter allows the read/write head to access any part of the platter
Can hard drives have more than one platter?
Yes, a lot of the time they are stacked on top of each other
Disadvantages of hard drives?
slow data transfer speeds and their
tendency to become damaged by movement
Why are hard drives delicate?
The combination of brittle platters and
moving parts results in a delicate device
How does magnetic tape work?
Wound onto reels, long stretches of
tape were passed through readers which would check the polarity of the tape and
read off a binary value
Disadvantages of magnetic tape
Bulky
What is a floppy disk?
a thin magnetic disk enclosed in plastic to protect the disk from dust and dirt
Advantages of floppy disks?
They were incredibly portable
Why were floppy disks portable
Think size and low weight
How does flash storage work?
The technology makes
use of silicon semiconductors forming the logic gates NAND
and NOR to store electrical charge in one of two states: high
or low
What is information stored in for flash storage?
Blocks
Logic gate used in flash for small quantities of data?
NOR
Logic gate used in flash for larger quantities of data?
NAND
What are blocks combined to form?
Pages
Can flash memory be erased?
Yes it can be erased and reprogrammed electronically
Is flash memory volatile?
No
Why are SSD’s resistant to damage?
No moving parts
Are SSD’s light?
Yes
Are SSD’s fast?
Yes
Disadvantages of SSD’s
Expensive and lifespan as ever time a page is written the voltage required to write it increases until it cannot be written anymore
Disadvantages of virtual storage?
Limitations of a user’s network and expensive
What is cloud info stored on?
100s of hard drives or SSD’s formatted to act as a single piece of storage
What is a program?
A collection of instructions
