BIOS and UEFI – CompTIA A+ 220-901 – 1.1

Before your operating system starts, the BIOS is in charge of your computer. In this video, you’ll learn about the BIOS features in your computer and the latest generation of UEFI BIOS software.

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When you first start up your computer before it loads an operating system, or it does anything relating to Windows, or Linux, or Mac OS, it first runs some software called the Basic Input/Output System. This is the starting point for everything else that runs on your computer. Even if there were no storage devices in your computer and no operating systems at all, you would still be able to run the Basic Input/Output System. You may hear this referred to as the firmware, or the System BIOS, or the ROM BIOS. There’s ROM or flash memory. All of these are similar names we use to describe this Basic Input/Output System.

The first thing that the BIOS does is initialize your system. It makes sure that you have all of the hardware components needed to continue with loading an operating system. So it checks to see if you have a CPU installed and if that CPU is performing properly. It checks the memory, and makes sure that you have memory installed onto your motherboard, and does a basic check of the hardware. We call this basic check a Power-On Self-Test, or a POST.

And if any of these very quick hardware checks fail for any reason, it’ll pop up a message on the screen telling you that there’s a problem with your CPU or with your memory, and then prompts you for correcting that particular issue. After it finishes the Power-On Self-Test, it then goes to your storage devices and looks for a boot loader that it can then use to hand off to the operating system, and your computer can continue to load your operating system normally.

That BIOS software has to live somewhere on your motherboard. And if you’ve got your motherboard documentation, it probably has a block diagram of the motherboard. And it will show you where the BIOS chip happens to be. You may want to open up your system and see if you can identify where the BIOS is. That’s what I did with my motherboard.

This is one that I have in my studio. You can see there are some PCI Express slots on here. You’ve got a battery that’s used– we’ll talk more about the battery in a moment– some other chipsets. And then there’s a very small chip right here on the right side, right here in the middle. And if we zoom up on that, you can see the words BIOS are written right on the chip. I couldn’t even find it. I needed to go to my motherboard manual to show me exactly where this was. And if you look close enough, you’ll be able to find that chip somewhere on your piece of hardware.

Whenever you start up your computer, there are going to be one of two different kinds of BIOS that may run. One is the legacy BIOS, and there’s also a newer type of BIOS called the UEFI BIOS. The legacy BIOS has been around for a very long time, for over 25 years. If you’ve worked with computers at all during that time, you’re probably accustomed to seeing this very familiar BIOS screen. It’s all text. And you can see that you can configure different settings inside of the hardware from this frontend. It’s a piece of technology that allows operating systems, in some cases, to talk directly to hardware. Although these days, the operating systems tend to use device drivers that then communicate with the hardware. But very early on in computing, we were able to talk directly to hardware through this BIOS.

There’s usually a limited amount of hardware these legacy BIOS systems will understand. This legacy BIOS doesn’t know that a network card is connected to your system. You can’t browse the internet or download files, because there’s no way to do it inside of this legacy BIOS.

The modern kind of BIOS that we find on all of our new systems these days is the U-E-F-I BIOS, or the UEFI BIOS. This stands for the Unified Extensible Firmware Interface. And it’s based on the standard from Intel called the Extensible Firmware Interface. Manufacturers will take this standard, and they’ll create a Basic Input/Output System frontend specific to their hardware. And what they’re doing is following this standard that is used across all different manufacturers’ systems. This is effectively replacing that legacy BIOS. You’ll no longer see the legacy BIOS being used, and we’ll use the UEFI BIOS for all of our modern systems.

When you’re using a modern UEFI BIOS, you now have a number of new capabilities. One of its bigger advantages is booting from larger and larger storage systems. We have very large hard drives and very large storage systems these days. And having a BIOS that can support these very large GUID partition table, or GPT disks, is very important. The BIOS can also support the legacy FAT formats. It can support booting from removable media. And these are capabilities we simply didn’t have with the legacy BIOS.

The UEFI BIOS also provides a pre-boot environment. This is something that we can use when troubleshooting the computer before the operating system has even loaded. If we’re having problems with the operating system, we can use this pre-boot environment to be able to go to a command line, to transfer files onto a storage device, to even bring up a browser and browse the internet and be able to communicate over the network. The UEFI BIOS frontend usually has some remote diagnostics as well. So someone can start up their UEFI BIOS, and you can connect to it remotely to see what’s going on inside of that computer without any additional software or operating system.

When you’re making all of these configuration changes inside of your BIOS, there needs to be a place to store all of these configuration settings. We’ve traditionally done this by storing it in non-volatile BIOS memory. This takes all of your settings that you’ve been working on and keeps them inside of your computer. We used to save this to a type of memory called the complementary metal-oxide semiconductor, or the CMOS. And we’ll very often still refer to it as CMOS memory, even when it isn’t. These days, we’re using flash memory to store this information and not the older CMOS.

One of the disadvantages of CMOS is that you have to have some type of power source to always keep your configuration settings active inside of that memory. If you lost the power, it would lose all of the settings. That’s why these days, we tend to use flash memory to store this information. It doesn’t need a constant power source, and it’s much more flexible and reliable when it comes to storing our BIOS configurations.

If you’re working with an older motherboard, you’ll probably see a battery like this somewhere on the motherboard. And it’s being used to provide that constant power to maintain your BIOS settings. If you unplug your computer and you move it to another location and plug it in again, it will still retain your BIOS configurations because this battery was there. Even on newer motherboards, you may still see a battery somewhere. It’s used these days to maintain the date and time, so that you don’t have to constantly reset that every time you turn on your computer.

If this battery goes bad and it’s being used to maintain the BIOS settings, then what you’ll find is that you’ll get a message every time it boots up that says, all of your BIOS settings are now removed. You have to now go back into the BIOS and make sure all the configuration settings are correct so that you could then start your computer. And you’ll have to do that every time you power up your computer.

On older systems, you used to be able to reset everything in the BIOS then by simply removing the battery. If you wanted to reset your BIOS after making an incorrect configuration, or you wanted to remove some of the passwords that were stored inside the BIOS, that was a very easy way to reset everything back to factory defaults.