11. OCR A Level (H046-H446) SLR3 - 1.1 RAM and ROM

Summary

This video script explains the roles of RAM and ROM in a computer system. ROM, soldered to the motherboard, contains the initial instructions for hardware checks and loading the BIOS. It's non-volatile, retaining data when power is off. RAM, volatile and temporary, stores data and instructions for active programs. The script also details the boot process, starting from ROM's power-on self-test to loading the OS into RAM. It briefly touches on different ROM types, evolving from unchangeable to electrically erasable.

Takeaways

• 💾 The CPU fetches instructions from memory, which includes two main types: RAM and ROM.
• 🔩 ROM is a small piece of memory soldered to the motherboard and contains the first instructions for checking hardware and loading the BIOS.
• 📱 ROM is also known as firmware and can be changed in some systems, like game cartridges.
• 💻 RAM is a temporary storage for instructions and data for programs being executed by the processor.
• 🖥️ The operating system is stored on the hard disk but is transferred to RAM for faster execution.
• 🔑 ROM contains the bootstrap, a set of initial startup instructions, and is non-volatile, meaning it retains data when power is off.
• 🔄 RAM, on the other hand, is volatile and loses its data when the computer is turned off.
• 🛠️ The POST (Power On Self Test) is one of the first instructions executed from ROM, checking the hardware and preparing the system to load the OS.
• 🔄 The boot process involves loading the OS from the hard disk into RAM, which is managed by the BIOS and can be configured to check other drives.
• 📚 There are different types of ROM that have evolved over time, from non-changeable to electrically erasable and programmable.

Q & A

What are the two main types of memory in a computer system?

The two main types of memory in a computer system are RAM (Random Access Memory) and ROM (Read-Only Memory).

What is ROM and where is it located in a computer system?

ROM (Read-Only Memory) is a small piece of memory soldered to the motherboard. It contains the initial instructions for the computer to check if the hardware is installed correctly and to load the basic input/output system.

What is the term for the initial instructions stored on ROM?

The initial instructions stored on ROM are also known as the bootstrap software or firmware.

How can ROM chips be changed in some computer systems?

In some computer systems, ROM chips can be changed to alter the program being executed, such as in game cartridges and portable entertainment systems.

What is RAM and what is its primary function?

RAM (Random Access Memory) is a temporary storage of instructions and data for programs being executed by the processor. Its primary function is to hold data that is in use by the computer's CPU, including the operating system.

Why is RAM used instead of directly executing instructions from the hard disk?

RAM is used instead of directly executing instructions from the hard disk because accessing data from the hard disk is too slow. Instructions are transferred from the disk to the memory first for faster processing.

What is the role of ROM during the initial startup of a computer?

During the initial startup of a computer, ROM provides the bootstrap, a set of initial startup instructions that are read-only and have been burnt onto it during the manufacturing stage.

What is the difference between ROM and RAM in terms of volatility?

ROM is non-volatile, meaning the instructions remain even when the computer loses power. RAM, on the other hand, is volatile, and the instructions are lost when the computer is turned off.

What is the Power On Self Test (POST) and its role in booting up a computer?

The Power On Self Test (POST) is a program that runs when a computer first turns on. It is responsible for sending signals to all connected components, checking their functionality, and informing the CPU of their existence.

How does a computer know to load the operating system from the hard drive?

A computer knows to load the operating system from the hard drive after the POST checks are completed. The ROM passes the first set of instructions to the CPU, which then loads the operating system into RAM.

What are the different types of ROM and how have they evolved?

The different types of ROM include ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), and EEPROM (Electrically Erasable Programmable Read-Only Memory). They have evolved from being completely unchangeable to being changeable with special tools or electrically without removal.

Outlines

00:00

💾 Understanding ROM and RAM

This paragraph explains the roles of ROM (Read-Only Memory) and RAM (Random Access Memory) in a computer system. ROM is a small, non-volatile memory chip soldered to the motherboard that contains the initial instructions for checking hardware and loading the basic input/output system, also known as firmware. These instructions are crucial for the computer's startup process. RAM, on the other hand, is a volatile storage used for temporarily holding instructions and data for the processor. It's faster than accessing the hard disk directly, which is why operating systems and currently running programs are loaded into RAM. The paragraph also describes the process of a computer booting up, starting with ROM's bootstrap instructions, which initiate the power-on self-test (POST) to check connected components and prepare the system to load the operating system into RAM.

05:01

🔧 Deep Dive into Computer Boot Process and ROM Types

The second paragraph delves deeper into the computer's boot process, explaining how the BIOS (Basic Input/Output System) stored on the ROM or a CMOS RAM is combined with the BIOS on the hard disk to form the boot file, which is then sent to the main memory. It discusses how the operating system takes control, searches for configuration files, and eventually fully boots up, taking over the computer. The paragraph also explores the evolution of ROM types, starting from the original ROM that was unchangeable after manufacturing, to P-ROM (Programmable ROM) that could be programmed once, and EPROM (Erasable Programmable ROM) that could be erased and reprogrammed with UV light. The latest types, EEPROM (Electrically Erasable Programmable ROM), allow for in-situ reprogramming without special equipment. The paragraph concludes by emphasizing the importance of understanding the complexity of the boot process and the nuances of ROM technology.

Keywords

💡Central Processing Unit (CPU)

The CPU is the primary component of a computer that performs most of the processing inside the computer. It fetches instructions from memory and executes them. In the context of the video, the CPU begins its operation by accessing the ROM to initiate the boot process. The CPU is central to the computer's operation, as it is responsible for executing the instructions that allow the computer to function.

💡Memory

Memory refers to the computer's storage components that hold data temporarily. The video discusses two primary types of memory: RAM and ROM. Memory is integral to the computer's operation as it allows for the storage and retrieval of data that the CPU processes.

💡Read-Only Memory (ROM)

ROM is a type of non-volatile memory used in computers and other electronic devices. It contains data that is permanently stored even when the system is powered off. The video explains that ROM holds the bootstrap software, which includes the initial startup instructions for the computer. An example given is game cartridges, which use ROM to store game data.

💡Random Access Memory (RAM)

RAM is a type of volatile memory used to store data that is being used by the computer. The video emphasizes that RAM is where the operating system and currently running programs are held, as accessing data from the hard drive directly would be too slow. RAM is central to the video's theme as it illustrates the temporary storage needed for the computer's operation.

💡Bootstrap Software

Bootstrap software, also known as firmware, is the first software that runs when a computer starts up. It is stored in ROM and is responsible for performing hardware checks and loading the basic input/output system. The video describes the bootstrap software as a critical part of the computer's initial startup sequence.

💡Firmware

Firmware refers to the low-level software that provides control for the device's specific hardware. In the video, firmware is mentioned as the software stored on ROM, which is used to check the hardware and load the operating system. It is an essential component in the boot process of a computer.

💡Non-Volatile

Non-volatile memory refers to storage technologies that retain data even when not powered. ROM is described as non-volatile in the video, meaning the instructions within it remain intact even when the computer is turned off, which is crucial for the computer's boot process.

💡Volatile

Volatile memory is a type of storage that loses its data when the power is turned off. RAM is highlighted as a volatile storage medium in the video, which means that any data stored in RAM is lost when the computer is powered down, emphasizing the need for a non-volatile storage like ROM for critical startup instructions.

💡Power On Self Test (POST)

POST is a series of tests run by the computer when it is powered on to check the integrity of its hardware. The video explains that one of the first instructions passed from ROM to the CPU is POST, which is responsible for sending signals to connected components to check their functionality. POST is a critical part of the boot process described in the video.

💡Hard Drive

A hard drive is a non-volatile storage device that stores and retrieves digital information using magnetic storage. The video mentions that while the hard drive is a long-term storage solution, it is too slow for the CPU to execute instructions directly from it, hence the need for RAM to temporarily hold data for processing.

💡BIOS

BIOS stands for Basic Input/Output System. It is firmware that is stored on a chip on the motherboard and is the first software the CPU accesses when the computer is turned on. The video discusses how BIOS works in conjunction with the bootstrap software in ROM to initiate the boot process, including checking for BIOS on the hard disk or CMOS RAM.

Highlights

The CPU fetches instructions from memory.

There are two main types of memory in a computer system: RAM and ROM.

ROM is a small piece of memory soldered to the motherboard.

ROM contains the first instructions for checking hardware and loading the BIOS.

The instructions on ROM are also known as bootstrap software or firmware.

Some ROM chips can be changed to update the program being executed.

RAM is a temporary storage for instructions and data for programs being executed.

RAM holds the operating system when the computer is running.

The computer's initial startup instructions are stored in ROM and are non-volatile.

RAM is volatile, and its contents are lost when the computer is turned off.

The bootstrap in ROM initiates the computer boot process.

The POST (Power-On Self-Test) is one of the first instructions executed by the CPU.

The BIOS is loaded into RAM from the hard disk after POST.

The operating system is stored on the hard disk but loaded into RAM for execution.

The computer's BIOS can be configured to check other drives first for booting.

The operating system takes control after being loaded into RAM.

Different types of ROM have evolved over time, from ROM to EEPROM.

EEPROM allows for electrical erasing and reprogramming without removal from the computer.

Transcripts

the central processing unit fetches

instructions from memory

there are two main types of memory in a

computer system also known as primary

storage

in this video we explore ram and rom

[Music]

the rom is a small piece of memory

soldered to the motherboard

it contains the very first instructions

for the computer

to check the hardware's installed

correctly and to load the basic

input output system these very first

instructions are also known

as the bootstrap software stored on the

rom is referred to as firmware

in some computer systems rom chips can

be changed in order to change the

program being executed

an example of this are game cartridges

and portable entertainment systems

the ram is a temporary storage of

instructions and data for programs

that are being executed by the processor

although the long term storage is

usually on the hard disk it would be too

slow to execute instructions from there

therefore they're transferred from the

disk to the memory first

the ram also holds the operating system

when the computer is running

here we see four important internal

components of a computer system

rom the cpu ram and a hard drive of some

description

when your computer very first turns on

and receives power

there are no instructions in the cpu

what it needs to do is load the

operating system so you can start using

it

of course the problem with this is that

the operating system is stored

on the hard drive and at the moment your

computer turns on

it doesn't even know the hard drive

exists let alone that it should look

there

to find the operating system and load it

into ram

the solution as explained earlier is rom

it contains the bootstrap a set of

initial

startup instructions placed on it during

manufacturing

the rom essentially contains a fixed set

of instructions which are read-only

and have been burnt onto it during the

manufacturing stage

now the important thing to note here is

that rom is what is known

as non-volatile and that means when the

computer uses

power the instructions in it remain

now this is very different from ram

which is a volatile storage medium

when the computer is turned off or the

instructions are lost

this means when your computer boots up

it can go to rom

find this set of initial startup

instructions and begin the process of

booting up your computer

one of the first set of instructions

passed from rom to the cpu

is what's known as the power on self

test or

post this program is responsible for

sending

signals to all the various connected

components it wakes them up it checks

their working

and essentially tells the cpu that these

other devices

exist

now our computer is aware of the hard

drive and the software stored on it

it can go ahead and load these

instructions into ram

and start the process of booting up your

operating system

so having watched this video you should

be able to answer the following key

question

what are the characteristics of rom and

ram

so that's where the specification ends

you can stop taking notes

but if you'd like a little bit of a

deeper understanding of how your

computer

actually boots up and some of the

different types of rom that are actually

in use today

then carry on watching so what actually

happens the moment your computer turns

on

right up to the point where you are in

your operating system and have control

well let's step through and have a look

well first of all we know the only place

where instructions can be fetched from

initially

is the rom as this is read-only memory

and has the set of initial startup

instructions

written into it at the manufacturing

stage nothing exists in ram at this

point

and indeed as we said earlier the

computer isn't even aware your hard

drive exists

one of the first things your rom does is

run the power on self-test

it checks that all the required

components are present

and are available it actually clears

anything

that may still be in the registers of

the cpu now of course

these are volatile there would be

nothing here but it's a safety step

that's done anyway

it loads the address of the first

instruction

in the boot program into the program

counter

at this point control is now passed to

the bootloader program

also known as the bootstrap which

carries out its

own checks on the hardware

it checks for any bios on the hard disk

or a storage device called a cmos ram

and bios is something we look at in more

detail in a later video

it combines this with the basic bios

stored on the rom

and then sends this to main memory

this file of information is known as the

boot file

the computer is now essentially ready to

load up your operating system

now the operating system is normally

found on the hard disk

but the computer's bios can be

configured in such a way

so it can be changed to check other

drives first

this will allow you for example to boot

a computer which has become corrupt

off a usb pen or an optical drive

the operating system itself is now

starting to take control

it searches for various other files for

example a config.sys

it tells it how many files can be opened

at the time which device drivers to load

the operating system may look for

additional files for example command.com

which contains additional information

about bios and various

operating system utilities

eventually the operating system is now

fully booted up and takes control of the

computer

the memory and loading jobs into the

processor

this is the point where you're able to

take over

now this process here is still highly

abstracted

and indeed it'll be different depending

on the actual system you're using

some of the files for example we've

referred to on the right like config.sys

and command.com

are typical for a windows boot up system

but not necessarily applicable to others

but it gives you an idea of the complex

nature of tasks that has to go on

when your computer is first powered up

before you're able to gain control

now earlier in the video we talked about

rom and we said it was read only

but there are different types of rom and

they've evolved over time

they all share a couple of things in

common they're non-volatile

and all the data is either completely

unchangeable meaning it's read-only

or it's changeable but requires a

special operation to do so

so the earliest version was simply

called rom read-only memory

the programming of data for the rom had

to be complete when the chip was

actually created and manufactured

and it couldn't be reprogrammed or ever

rewritten

an evolution of this was then called

p-rom or programmable read-only memory

as the name suggests this memory was

able to be purchased

from the manufacturer and then coded

once with a special tool known as a

programmer

this was known as burning the prom this

meant that the manufacturer could

actually release

blank roms

a further evolution was a raisable

programmable read-only memory now these

were the first roms which could be

rewritten

many times however erasing them required

a special tool

that omitted a very certain frequency of

uv light

and the rom would actually have to be

removed from the device

before it could be erased and

reprogrammed

some of the latest evolution of roms are

the electrical

erasable programmable read-only memory

now this chip doesn't have to be removed

from the computer in order to have its

contents rewritten

the entire chip also doesn't need to be

completely erased

to change the specific portion of it and

also changing the contents does not

require any specialist equipment

now as we said for your exam you should

simply think of rom

as being read-only and unchangeable

but it's useful to understand that even

in this area of technology things aren't

that simple

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