BIOS and UEFI settings for CompTIA A+ Core 1

What is motherboard firmware, and how does UEFI differ from BIOS?

Motherboard firmware is the low-level software baked into a chip on the board. It wakes the hardware up, runs a quick self-check, and hands control to your operating system. BIOS is the original version of that firmware. UEFI is the modern replacement you will find on nearly every current machine.

BIOS stands for Basic Input/Output System. When you power on, it runs the power-on self-test, or POST, to confirm the CPU, memory, and drives respond, then it finds a bootloader and steps aside so the operating system can take over. The code lives in flash memory on the motherboard, which is why firmware can be updated rather than replaced.

UEFI, the Unified Extensible Firmware Interface, does the same job with real advantages. It gives you a graphical screen you can drive with a mouse, it boots faster, and it supports drives larger than about 2.2 TB by pairing UEFI mode with a GPT partitioned disk instead of the older MBR scheme. For the full picture on GPT and boot drives, see our guide to SSDs, HDDs, and RAID. On the exam this all sits in Domain 3.0 Hardware, about a quarter of CompTIA A+ Core 1, under objective 3.5 on installing and configuring motherboards, CPUs, and add-on cards. Most techs still say BIOS out of habit, even when the firmware is really UEFI.

Getting into firmware takes the right key at the right second. Delete, F2, F10, and Esc are the usual choices, and the vendor often flashes the correct one on screen at startup.

How do boot order and boot mode decide what starts?

Boot order, also called boot device priority, is the list your firmware walks through to find something to start: internal drive, then USB, then network, in whatever order you set. You change it when a machine needs to boot from a USB installer or a recovery tool instead of its usual drive.

Many machines also offer a one-time boot menu, often on F12, that lets you boot a USB once without permanently reordering anything. When you are just running a tool and want the normal order back afterward, that is the cleaner move.

Boot mode is the other half. UEFI mode is the modern default and expects a GPT disk. Legacy mode, usually labeled CSM for Compatibility Support Module, lets a newer board boot an older MBR-style, BIOS-era operating system. The two schemes do not mix on a single install. If a drive was set up for one mode while the firmware is set to the other, you get a confusing no bootable device message even though the drive is perfectly healthy. A technician switches boot mode when an OS refuses to install or a known-good drive will not start.

One habit worth building: after you install an OS in UEFI mode, the firmware remembers a named boot entry for it, so a healthy machine can show the OS by name in the boot list. If that entry disappears, it is a strong hint the drive, the partition, or the boot mode changed, not that Windows itself is gone.

What do Secure Boot, TPM, and the BIOS password actually do?

These three settings protect the machine at the firmware level: Secure Boot checks that boot software is digitally signed, the TPM stores encryption keys, and a BIOS password locks the firmware menu so nobody can quietly change either one.

Secure Boot is a UEFI feature. Before anything loads, the firmware checks the digital signature of each piece of boot software against keys it trusts, which helps block rootkits and bootkits that try to run before the operating system. You sometimes turn it off to dual-boot a Linux distribution whose bootloader your firmware does not recognize. Many mainstream distros work with it on today, though some setups still need it off. A careful tech disables it only for a clear reason, then turns it back on.

The TPM, or Trusted Platform Module, is a small tamper-resistant crypto chip, sometimes built into the CPU as firmware, which AMD calls fTPM and Intel calls PTT. Its headline job for A+ students is BitLocker: the drive-encryption key lives in the TPM, so the disk only unlocks when the boot state looks untampered. Windows 11 requires TPM 2.0, so enabling it in firmware is now routine. One caution: clearing the TPM wipes those keys, so if BitLocker is on, have the recovery key ready first.

The BIOS or supervisor password locks the firmware settings themselves. Without it, someone could reorder the boot devices or switch off Secure Boot in under a minute. That is different from a power-on password, which is required just to start the machine, and different again from your Windows sign-in.

Virtualization, fan monitoring, and the battery that keeps time

The rest of the firmware menu is about daily reality. You turn on CPU virtualization to run virtual machines, you watch temperatures and fan speeds, and a coin-cell battery quietly keeps your clock and settings alive.

CPU virtualization goes by brand names: Intel VT-x and AMD-V, which some boards label SVM Mode. It often ships switched off, and you enable it before running virtual machines in Hyper-V, VirtualBox, or VMware, and for Windows features like WSL and some Android emulators. If a virtualization app complains that hardware acceleration is unavailable, this toggle is the first thing to check. That connects straight to Domain 4.0, Virtualization and Cloud Computing, on Core 1, so it is worth knowing where the setting lives. You can rehearse settings like this in study mode before you open a real machine.

The hardware monitor page shows live CPU temperature and fan RPM, and it can let you tune a fan curve so the system runs quieter or cooler. When a computer overheats or a fan sounds like a jet, this screen is the first calm place to look before assuming a failed part.

Finally, the CMOS battery. This is a CR2032 coin cell that keeps the real-time clock running and, on many systems, preserves firmware settings while the PC is unplugged. When it dies, the clock resets to an old default date, you may see a CMOS checksum error, and settings drift back to stock. Some machines even pause at every boot asking you to load defaults until it is replaced. The fix is a cheap coin cell, and a tech swaps it when the date will not stay put.

When does a technician actually change these settings?

Most of the time, you leave firmware alone. You open it for specific jobs, and the exam rewards you for knowing which setting maps to which job. None of these are things you change for fun; each one has a trigger. Here is the quick field version.

• Boot order or one-time boot menu: booting a USB installer, a recovery drive, or a diagnostic tool.
• Boot mode, UEFI versus CSM: an OS will not install, or a drive was partitioned for the other scheme.
• Secure Boot: turned off to dual-boot an unsigned Linux loader, then turned back on.
• TPM: enabled for BitLocker or to meet the Windows 11 requirement.
• Virtualization, VT-x or AMD-V: turning on virtual machines, WSL, or emulators.
• BIOS or supervisor password: locking firmware on a shared or public machine.
• Fan and temperature monitoring: chasing heat, noise, or throttling complaints.
• CMOS battery: the clock keeps resetting or settings will not stick.

The firmware menu is more approachable than it looks

Firmware is just a settings screen that happens to run before Windows. Learn the same handful of controls the exam cares about: boot order and boot mode, Secure Boot, TPM, the virtualization toggle, passwords, fan and temperature monitoring, and the CMOS battery. Objective 3.5 does not ask you to memorize every menu on every board. It asks whether you understand what each setting does and when a technician would change it. So open the firmware on a machine you own, read the menus without changing anything, and match what you see to the terms here. If you want reps in a safe place first, walk through it in study mode. Do that once and BIOS UEFI settings stop being trivia and start being a place you already know your way around.