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.
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.
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.
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 recommendations.....
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
This is to do with 32bit limitation. With MBR (Master Boot Record) it can only access up to 2TB. In order to access more the BIOS needs to support GPT which is 64-bit. Some 32-bit BIOS can access 64-bit, where others can't. Since the BIOS provides the initial code, that is accesses the hard disk to load the boot loader, if it can't access a GPT drive it won't be able to boot. When the computer starts up, the BIOS code essentially get replaced by the operating system code which can access above 2TB, thus why it can now access data drives where before it could not.
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?
The CPU is required to make beep nosies. The CPU can execute code directly from the BIOS which it needs to be done initially. Since the CPU has cache and registers etc, it can execute a small amount of code directly from the BIOS without the need for memory. This is not viable for long term use, so when the start up gets far another in the BIOS ROM is copied into memory and run from there. So in the very early stage the BIOS code is been executed from the BIOS.
[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 ?
The best way to do this is to have a motherboard that supports it. If your motherboard does not, you can try a some software like ClockGen that may allow you to change a few settings and get some extra speeds.
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.
In the old days this was correct. In the 1980 they developed shadow BIOS which copies the BIOS in memory as ROM is slower than main memory. In the 1990s with the the 386 and 486 having more memory it became common place to shadow the BIOS into memory. However, most BIOS would allow you to disable it if you wanted. As time when on, this feature was removed and thus the BIOS was always shadowed and you could not switch it off. Have a think about it logically. Would you really want a BIOS chip connected by a bus like the low pin count (LPC) to be directly accessed by the CPU running flash memory on a computer with fast CPU and memory? It does not make sense on more computers.
The one thing still not clear for me if BIOS has it's own CPU? Does it? Seems it does but this CPU is very primitive and serve mainly to setup and launch more advanced CPU. Is it correct?
The BIOS only contains code and small amount of settings. When the computers starts up the CPU either runs codes directly from the BIOS or the BIOS code is copied to memory and run from there. BIOS only performs very primitive operations and thus is used to boot strap an operating system to run more advantaged functions.
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 ?
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.
Over 2TB requires GPT. GPT generally requires a 64bit operating system to boot off. Thus, a lot of systems requires UEFI to boot off but not all. This video explains it in more detail. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ZOjicsRClic.html
The CPU is running the instructions for the BIOS and the boot loader. Essentially the computer needs some software to run, the BIOS provides this initial software before control is passed to software like the boot loader.
