11. OCR A Level (H046-H446) SLR3 - 1.1 RAM and ROM
Summary
TLDRThis 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
💾 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.
🔧 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.
Mindmap
Keywords
💡Central Processing Unit (CPU)
💡Memory
💡Read-Only Memory (ROM)
💡Random Access Memory (RAM)
💡Bootstrap Software
💡Firmware
💡Non-Volatile
💡Volatile
💡Power On Self Test (POST)
💡Hard Drive
💡BIOS
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
[Music]
you
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