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Chip 101
Lesson 11 of 36 ยท Inside a modern processor

What are BIOS, firmware and drivers?

Firmware is software built into hardware. The BIOS starts the computer; drivers let the operating system (OS), such as Windows, talk to each part.

  1. BIOSCPU corespower onflash chipruns it first

    1. Software built into hardware

    The BIOS (basic input/output system) is firmware in a flash chip: the first code the main CPU cores run. Small helper processors, such as the power manager, wake a moment earlier.

  2. POST checklistmemorygraphicsstorageUSB

    2. A check before opening

    Next, the BIOS runs a power-on self-test (POST): it checks and sets up memory and devices, like a worker checking the lights before opening.

  3. BIOSOSstartsACPI tablessleep statesspeed settings

    3. Handing over to the OS

    Then the BIOS starts the operating system (OS), such as Windows or Linux. It also hands the OS the ACPI (Advanced Configuration and Power Interface) tables: a list of the chip's sleep states and speed settings.

  4. operating system (OS)drivergraphicsdriverWi-Fidriverchipset

    4. One driver for each part

    The OS talks to each part through a small program called a driver; a new printer needs one too. Graphics, Wi-Fi and the chipset that links USB and storage each need one.

  5. BIOS 2.1+driver 5.0worksBIOS 1.0+driver 5.0may fail

    5. Versions must match

    BIOS, firmware and drivers each have version numbers. A new driver may need a new BIOS, so the versions must match.

Words to know

Firmware
Software built into hardware, as in a TV or a microwave.
BIOS (basic input/output system)
The firmware that starts a computer and sets up its parts.
Flash chip
A memory chip that keeps its data when the power is off.
POST (power-on self-test)
The checks the BIOS runs on memory and devices at start-up.
ACPI tables
Notes from the BIOS that tell the OS which sleep states and speed settings the chip has.
Driver
A program that lets the OS use one kind of hardware.
Chipset
The parts that connect the processor to storage, USB and other devices. In an SoC, most sit inside the chip.

Where you meet it at work

Testers write down the exact BIOS, firmware and driver versions with every result, since one version change can change the outcome.

Check yourself

What is the first code the main CPU cores run after you press the power button?Think first, then tap to see the answer.

The BIOS, stored in a flash chip on the board.

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