Unit 1 Flashcards
(18 cards)
What is the purpose of the CPU
It is responsible for all the computers processing
What is the fetch decode execute cycle
FETCH: Causes the next instruction and any data involved to be fetched from the main memory
DECODE: decodes the instruction
EXECUTE: carries out the instruction
What are the 2 major components of the CPU, their functions
What is another component of the CPU
CU (Control Unit) - Coordinates all activities taking place in the CPU (ie : input/output of data, hardware attached, flow of data)
ALU (Arithmetic Logic Unit) - Where the actual calculations are done (ie: arithmetic operations and logical operations)
the 4 registers
What are the 4 registers of the CPU and their functions
Program counter (PC): Holds the address of the next instruction to be executed
Memory address register (MAR): Holds the memory address of the current instruction, and then the data that it uses, so that this can be fetched from the memory
Memory data register (MDR): Holds the actual instruction, and then the data that has been fetched from memory
Accumulator: Holds the result of an instruction before it is transported to memory
How are the MAR and MDR in sync
In the FETCH stage, the PC copies the address of the instruction to the MAR
The instruction at the address is fetched and copied to MDR
The CU decodes the instruction and decides if data needs to be fetched
If so the MAR is used to hold onto the address of the data to be used in the instruction
The data is fetched then copied onto the MDR
Factors affecting CPU performance and definitions
Clock speed - Cycles per second - Hz
Number of Cores - Num of duplicate processors linked together on a single chip
Cache size - Super fast working memory on the CPU
What is cache memory and the effect of speed on it
Small amount of very expensive memory and can be accessed faster than main memory (ie: RAM)
For frequently used instructions, cache memory is used to store it so they can be fetched quicker:
Level 1 cache is Really fast, Really small and On the CPU
Level 2 cache is Fairly fast, Medium sized and Fairly close to the CPU
What is an embedded system
A single microprocessor including RAM ROM and a CPU
What are the characteristics of RAM
RAM:
Main memory that can be read from and written to.
Access to it is very fast.
It contains running programs (ie: OS) and data when the computer is turned on
Because RAM is volatile, the data will be erased when the computer turns off
What happens when you run out of available RAM
Virtual memory is used: Part of the hard drive as an extension to RAM
It provides extra RAM for more programs but data on there will take longer to fetch
Characteristics of ROM
Some data needs to be permanently held onto memory, even when the computer is off (ie: initial instructions on turning on the PC)
This data is therefore non-volatile (doesn’t delete when PC is turned off)
What is secondary storage
Memory which is indirectly attached to the CPU (not directly connected to the CPU
Non volatile
they can be either internal or external to the PC
What are the 3 storage methods and how they work
Magnetic: Mechanical parts which move over the disks surface to read and write data magnetically or a drive head reads a magnetic tape
Optical: Lasers read and write data using light
Solid State: Data is recorded onto solid memory chips with no moving parts
Need for secondary storage types
Hard drive
Blu Ray
memory stick
magnetic tape/Hard drive
SD cards
Programs and data are stored here
Distribute films
Transport data from one place to the other
Backing up data
Additional storage on cameras/phones: Used for video games, music, photos etc
Magnetic storage: Adv, Dis, uses and capacity
Adv:
Cheap, large storage capacities, relatively fast read speed
Dis:
Lots of mechanical parts, durability, sealed unit due to disk head and not portable
Uses:
Personal computers, large quantities of data
Capacity:
500GB to 12TB+
Optical storage: Adv, Dis, uses and capacity
Adv:
Cheap, portable, takes up little space physically
Dis:
Less storage relatively
Easily damaged, requires CD reader
Slow write speeds
Uses:
Songs, games, Multi media storage, backup
Capacity:
CD: Up to 720MB
DVD: Up to 8.4GB (Dual Layered)
Blu - Ray: Up to 50GB (dual layered)
SSDs: Adv, Dis, uses and capacity
Adv:
Highly durable, no moving parts, fast read/write, little noise, fast start up
Dis:
More expensive than Magnetic while having the same storage
Uses:
High end PCs, Laptops, phones/tables
Capacity:
100BG - 12TB+F
Flash drive characteristics:
Low cost
Portable
Durable
No moving parts
makes them ideal for a range of offline devices:
Cameras
Mobile phones, USB memory sticks
