BIOS

This section of the ITFreeTraining courses will look at the BIOS. BIOS or Basic Input/Output System is the software that is responsible for initially testing and communicating with your hardware. Without the BIOS the computer would not start. This video will look at what the BIOS can do, upgrading the BIOS and how the BIOS works.

What is BIOS?
0:20 To start with, I will first look at what the BIOS is. Essentially, the BIOS is a microchip found on the motherboard. BIOS is essentially what is referred to as firmware. Firmware contains basic low-level software that controls the hardware in the device it is installed in. In the case of computers, the BIOS contains basic input and output software which is used to communicate with hardware. When the computer is first switched on, the BIOS software is used to test the hardware within and connected to the computer. Once complete, the software in the BIOS is used to access the hardware.

BIOS was first created in 1975 by IBM. It was later reverse engineered to be used in non-IBM computers. Nowadays there are three companies that make the majority of BIOS chips and IBM is not one of them. I will now have a closer look at what happens when a computer starts up, to give you a better understanding of how the BIOS works and what it does.

Powering Up PC
1:20 To start with, I will first look at what happens when the power button is pressed on a computer. When the power button is pressed, a circuit is closed which causes a test to be preformed of the computer’s power supply. If there is a problem with the power supply, usually there will be no power output at all and the computer will not start.

If the power supply test is o.k., the power supply will send power to the CPU. Now the CPU has powered up, it will start executing instructions, because that is what a CPU was designed to do. In order to do this, it needs software and this is where the BIOS comes into play.

Load BIOS Software
1:56 The BIOS is essentially a microchip on the motherboard. This is also often referred to as firmware. Older BIOS chips use Electrically Erasable Programming Read-Only memory called EEPROM, whereas modern BIOS uses flash RAM. This allows the code in the BIOS to be updated, but the code on the BIOS cannot be directly run from the chip itself.

In order for the CPU to execute the code in the BIOS, the code in the BIOS is copied to the memory inside the computer. So essentially this means that in order for a computer to start, it requires memory. If you attempt to power up a computer that does not have memory installed, the motherboard will emit a number of beeps to alert you that there is a problem.

Once the BIOS code has been copied to memory, the CPU can now start executing the code. So essentially what happens is this. When you press the power button, the code in the BIOS is copied to memory and then is executed by the CPU. The next question is, what does this code do?

POST Tests
2:57 The next step is that the BIOS performs a number of tests. These tests are referred to as POST or power- on self-test. These are a number of quick tests to check everything appears to be working. There may still be hardware faults, but the POST tests should pick up any basic problems.

POST tests include but are not limited to, checking the memory installed. This is a quick check to see if everything appears to be working correctly. There are a number of memory testing software tools available that can do more advanced tests if required.

Tests also include checks of any attached storage devices. This is basic testing to ensure the devices start up and are accepting commands. For example, a hard disk test would spin the drive up and test it to ensure the drive can be accessed.

Other checks include checking the keyboard. The check tests every key on the keyboard. Depending on the BIOS, if a stuck key is detected a warning message will appear.

Any devices like a mouse are also checked. This includes devices like trackpads and trackballs.

References

Credits

[itfreetraining]

There is one step we omitted to make it a bit easier to understand, but in hindsight we should have left it in.

In the old days, the BIOS was stored in a ROM chip. The ROM chip was slow compared wth RAM. However back than memory was expensive so the CPU ran code from the BIOS ROM even though it was slower..

As RAM size increased, they added an option called shadow BIOS. The CPU still run the code in BIOS, however when shadow BIOS is enabled, the BIOS will copy itself into RAM and run from there.

As time when on, since RAM was quite large, shadow BIOS was enabled BIOS by default. Later on, the option shadow BIOS was removed from BIOS and just left enabled.

So nowadays, the CPU still executes initially from BIOS or UEFI direct from the chip, but since shadowing is enabled, it will copy itself in RAM and run from there.

[yudarecht]

I listened to 10 videos about BIOS, this is the only one who really explained

[mtolives-wmsp]

I takes 3 minutes to understand the basis meaning of BIOS than my 1 years six months training in computer. Thanks ever so much for this great tutorial. God bless you.

[sra]

So far this is the best video I have found explaining the BIOS. Thank you!

[HonsHon]

So awesome! Really glad to be learning computer hardware in such a nice, concise, and helpful fashion.

[waynezahra]

Hi, good morning Sir. Wow, you have a great way of explaining and being direct with your explanation. There is only you and one other channel that I’ve found to be extremely informative without speaking in telephone numbers. Thank you ever so much for your time and making of this video. Your time hasn’t don’t unnoticed. I’ve found your video to be extremely informative.

[snail-bait]

First exposure to your content...really happy I found it. BIOS actually now makes sense 👍. Brilliant video.

[stonespider]

Very interesting list of playlist. People pay so much money and join classes to learn about computers but learn nothing as the faculty and teachers aren't capable of teaching.

People can learn so much more here, and easily grasp and understand via your explanations.

Will recommend others whoever I know who wants to learn about computers.

Btw... I got this video recommendation on my Google news feed in my Android phone.. Not even on youtube

[tedc]

Love the detail. This is my first of what I imagine will be binge watching your content

[t.m.]

Most important thing I learned from this video is that the plural of BIOS is BIOS

[ನಾಬರೆದೆ]

Thank u sir you are god for poor students

[badrdoctor]

Excellent IT Training Channel and very informative content.
I have a simple question though, if the BIOS need first to be copied by the CPU to the memory in order to be read and executed to launch the POST routine! what else then emits the error beeps of memory when it is faulty or not even installed?? The CPU Cach memory for example?

[nezmustafa]

When you say boot from storage devices larger than 2tb what difference does it make? I though the bios couldn't access any files and folders and the boot loader does. Are you talking about safe mode?
Thanks

[siddhisattur]

The BIOS is not loaded into the memory, it is already present in the flash memory and CPU is hard coded to understand the location of BIOS, it executed it directly from the flash memory.

[ocamlmail]

Great, thank you very much! Exhaustive explanation.

[billkillernic]

Something must have been omitted in the explanation how does the bios "know" to load itself to memory it must be the cpu seeking to do something like the first step it does every time it is reseted which probably is to tell the memory to copy the bios ?

[hitendrasharma]

i like to watch every video in.playlist. Thanks for sharing such knowledge.Please try to create videos on Azure Administration.

[rean_kmeannei]

EFI = UEFI ( Compatibility Support Module, Secure Boot, Larger Disk Support, Larger memory sizes, Better Graphical User Interface, Network Booting, Improved security )
UEFI Have = Faster boot times

[SoCloseKinG]

Sir i have a i5 650 and i want yo overclock it but (M I T) is not present in my bios feautures how can i access to mit please tell me

[madhavamng]

[non-related] bro, I bought a mother board, works fine, if I press the left arrow in keyboard It assiume the input as mouse's right click. and If I press backspace it assume alt+backspace. what can I do for it ?