Where Is BIOS Stored In Your Computer?
If you have ever examined the motherboard, you may have seen multiple Integrated Circuit (IC) chips soldered onto the motherboard. One of the IC chips contains the lines of code that hold the BIOS.
Just looking at the motherboard, you may not be able to locate the BIOS chip. Depending on the motherboard manufacturer, there could be any markings on the board that indicate the BIOS chip, such as M_BIOS, B_BIOS, UEFI BIOS, etc.
Where Is the BIOS Chip Located?
Two crucial chips are related to the BIOS. One is the CMOS EEPROM chip that holds the BIOS program, and another is the CMOS RAM chip that stores BIOS settings.
Note: BIOS settings include all the adjustable parameters in the BIOS.
The first one is the CMOS EEPROM (Electrically Erasable Programmable Read-Only Memory) chip that holds the BIOS program. This chip is usually denoted as M_BIOS or B_BIOS on the motherboard. But these notations are not universal. Depending on the motherboard manufacturer, the notation used to mark the BIOS location could be different.
So we recommend you check your motherboard’s user manual to check the actual notation for your motherboard that indicates the BIOS chip.
The second chip is the CMOS memory chip which holds the BIOS settings. These are volatile memory. Meaning that these chip will remove data inside it once you remove the power supply. So they require a separate power source to store the information once you turn off the system. This is done with the help of a CMOS battery.
The chip that stores the BIOS settings is usually near the CMOS battery.
How Does the BIOS Chip Work?
The IC chip that holds the BIOS is a non-volatile CMOS EEPROM chip. Meaning that the chip won’t lose data stored inside it even when you cut off the power supply. This is why the BIOS does not get deleted even when you remove the CMOS battery and turn off the power supply in your system.
BIOS is the first software the motherboard runs when you turn it on. Your motherboard is programmed such that the BIOS automatically runs as soon as it gets power. Once the BIOS runs, it checks necessary hardware to run the entire system.
When the system starts, the BIOS runs a POST (Power-On Self-Test). During POST, the BIOS checks and verifies all the hardware components connected to the motherboard.
These components include RAM, CPU processor, Input-output Controller Hub, graphics card, keyboard, mouse, etc. If the BIOS fails to detect crucial hardware components, such as the CPU and RAM, the motherboard sends beep codes indicating component detection failure.
Once the BIOS completes POST, it checks storage devices for an Operating System and then loads it into the RAM.
How are BIOS Settings Saved?
All your BIOS settings, like current, voltage requirement, frequency, fans RPM, etc., are stored in a volatile memory chip, usually called CMOS chip. CMOS stands for Complementary Metal Oxide Semiconductor and is the technology used in most IC chips.
Being a volatile memory, CMOS will not save its data if you remove the power supply. In our case, where all BIOS settings are inside the CMOS chip, it will also require a separate power source.
This is done via a separate battery on the motherboard, named the CMOS battery. CMOS battery provides constant power to the CMOS chip so that data inside the CMOS chip stays even if you turn off the power supply to the motherboard. If you remove the CMOS battery or it runs out of power, all the BIOS settings will be set to its default state once you turn off the system.
Is BIOS and CMOS the Same Thing?
BIOS and CMOS are not similar at all. BIOS is a program that the motherboard first runs once you turn on the PC. This program is stored in a separate EEPROM chip on the motherboard. On the other hand, CMOS is a metal-oxide-semiconductor that holds a small amount of memory.
The BIOS uses the CMOS chip to store user-preferred settings and hardware information about the components connected to the system.