【My Study Note】BIOS
BIOS
How do external devices like a mouse or keyboard talk to the CPU? Because they don’t have any instructions that our CPU knows how to read.
Drivers
If you just clicked on the key from your keyboard, you’d only be sending a byte to the CPU. But the CPU doesn’t know what this is, because it doesn’t have instructions on how to deal with it.
That’s why our devices also use programs to tell the CPU how to run them. These programs are called services or drivers. The drivers contain the instructions our CPU needs to understand external devices like keyboards, webcams, and printers.
BIOS (Basic Input Output Services)
Our CPU doesn’t know that there is a device that it can talk to, so it has to connect to something called the BIOS. The BIOS is software that helps initialize the hardware in our computer and gets our operating system up and running.
Where the BIOS is stored?
The BIOS isn’t stored on a hard drive. Our motherboard stores the BIOS in a special type of memory called, the read-only memory chip, or ROM chip.
Unlike RAM, ROM is non-volatile, meaning it won’t erase the data if the computer is turned off. Once the operating system loads, we’re able to load drivers from non-essential devices, directly from the hard drive.
UEFI (Unified Extensible Firmware Interface)
In today’s system, there is another player for BIOS called UEFI. UEFI performs the same function of starting your computer as a traditional BIOS. But it’s more modern and has better compatibility and support for newer hardware.
POST (Power On Self Test)
When you turn on a computer, you might notice a beeping from time to time. How computers run a test to make sure all the hardware is working correctly. This is called a POST. And then BIOS runs it when you boot up your computer.
The POST figures out what hardware is on the computer. So it happens before the BIOS initializes any hardware or loads up essential drivers. If there is an issue with anything at that point, there is no way to display it on the screen, since things like the video driver haven’t been loaded.
Instead, the computer can usually produce a series of beeps, almost like Morse code, which will help identify the problem. Different manufacturers have different beep codes. So, if your computer successfully boots up, you may hear a single beep. If you hear two beeps, it could mean a POST error. It’s best to refer to your motherboard manual to find out what each code means. Also, you should know that not all machines have built-in speakers, so don’t worry if your computer boots without a beep. But if there is it’s so helpful when you troubleshoot it.
CMOS battery
To conduct the BIOS settings, there is a special chip on our motherboard called the CMOS battery. It stores basic data about booting your computer like the date, time and how you wanted to start up.
You can change these settings by booting into CMOS or BIOS setting menu. It varies in different computers, but usually when you boot the computer, there will be a quick screen that tells you what button to push to get into the settings. From there, you can change the basic BIOS settings of your machine.