1.2.1 Primary storage

Primary storage

Known as main memory or primary memory

It is volatile

Can be accessed directly by the CPU

Secondary storage

This type of storage cannot be read directly by the CPU.

It's non-volatile and much bigger than primary.

Examples are Hard Disk, USB Flash Drive, SSD, CD

Random Access Memory

Primary Storage we can write to, also known as main memory.

All data in use and instructions currently running are stored here.

It is volatile.

Easily expandable//can add more if needed

RAM uses

Stores the parts of the OS / programs that are running…

Stores the data currently in use

… for access by the CPU

Increasing RAM - impact on performance

More instructions / programs / applications can run at the same time / be held in RAM

Open software faster / respond faster

More memory space for current programs

Run more memory intensive programs e.g. computer games / graphic rendering

reduces use of Virtual Memory

…..less use of hard drive which is slower to access

Other than RAM - other ways to improve computer performance

Increase processor clock speed (overclock)...

...Run more FE cycles per second

...Faster response

...Smoother actions

...Less likely to freeze

Add more cores

...Run more tasks simultaneously

...Better performance for programs that are programmed for multi-core systems

E.g. new computer games

Increase cache size

...Cache stores frequently used instructions / programs / data

....Can store more so increase access speed to more frequently used instructions / programs / data

New graphics card

...Can carry out more processes for CPU

...Can improve speed and quality of graphics

Change hard disk drive to SSD

...faster read / write speed

Read Only Memory

Cannot be changed.

Stores the boot program / bootstrap loader / BIOS

Non-volatile semiconductor primary memory

Contains the start-up instructions for the computer known as the BIOS

RAM vs ROM

ROM is non-volatile and RAM is volatile

RAM is easily expandable, ROM size is (usually) fixed for a given computer

Contents of RAM change frequently, contents of ROM never (hardly ever) change.

RAM vs Flash/Solid State memory

RAM is volatile // Flash memory is non-volatile

RAM is faster to access/store data than Flash memory // Flash memory is slower to access/store data than RAM

RAM stores currently running programs/instructions/data/OS // Flash memory stores files and software

RAM can be directly accessed by CPU // Flash data has to go to RAM before CPU

Volatile

Data is lost when computer is powered off, RAM is this type

Process

Any part of a program that is currently running, this will need to be in primary memory so the CPU can execute it

Non-volatile

Data is retained when powered off, ROM/HDD/SSD is this type

BIOS

The startup instructions for a computer, stored in ROM.

It stands for Basic Input Output System

Virtual memory

Using the hard disk / secondary storage...

...Used as RAM / to store the contents of RAM / main memory...

...Needed when there isn't enough physical memory

Secondary/virtual storage has slow access speeds than Primary Memory (RAM)

Swapping

Moving a process from RAM to virtual memory to make more room in RAM for a new process

Thrashing

Constantly swapping processes between RAM and virtual memory because there is not enough RAM.

Causes slow performance.