What is BIOS & UEFI?

What firmware actually does

Press the power button. Long before Windows shows up, a tiny chip on your motherboard runs the firmware. It does four things in roughly half a second:

• POST (Power-On Self Test). Counts the RAM, identifies the CPU, checks that the GPU responds and the storage devices are present.
• Hardware initialisation. Trains the memory at the correct speed, configures PCIe lanes, sets fan curves and assigns IRQs.
• Loads the boot order. Looks at which drive is set as #1, finds the Windows Boot Manager (or Linux GRUB) and hands over.
• Exposes a settings menu. If you tap DEL or F2, it pauses and shows the BIOS interface instead of booting.

That's it. Once Windows takes over, the firmware steps back and does nothing — until next power-on.

BIOS vs UEFI — the modern distinction

Strictly speaking, BIOS is the legacy standard (16-bit, blue-text-on-grey, keyboard-only) from the 1980s. UEFI is the modern replacement that took over from roughly 2012 onward. Everything sold today is UEFI — people just still say "BIOS" out of habit.

Modern UEFI implementations from ASUS, Gigabyte, MSI and ASRock all offer two modes: EZ Mode (the dashboard view, where 95% of users will live — XMP toggle, boot order, fan curve, that's it) and Advanced Mode (the deep menu tree where overclockers spend their evenings).

How to enter the BIOS

Power on the PC. During the brief POST splash (motherboard logo or text), tap the entry key repeatedly — not once and hope, but every quarter-second until the BIOS appears.

• ASUS, Gigabyte, MSI, ASRock desktops: DEL is the universal entry key.
• Dell, HP, Lenovo laptops: F2 most common. F10 on some HP. F1 on older ThinkPads.
• Acer, Samsung, Razer: F2 mostly.
• One-time boot menu (without entering BIOS): F12 on most boards, F8 or F11 on others.

If Fast Boot is enabled in Windows and the POST splash is too brief to catch: go to Windows Settings → System → Recovery → Advanced startup → Restart now → Troubleshoot → Advanced options → UEFI Firmware Settings → Restart. The PC reboots directly into BIOS.

The settings that actually matter

XMP / EXPO — unlock your RAM speed

By default, DDR5 boots at the conservative JEDEC base speed (typically 4800 MT/s) — regardless of whether you bought 6000, 6400 or 8000 MT/s rated memory. XMP (Intel) and EXPO (AMD) are pre-configured profiles stored on the RAM kit that unlock the speed printed on the box. Enable it; this isn't risky overclocking, it's getting what you paid for.

Secure Boot — leave it on

Secure Boot verifies the digital signature of the Windows Boot Manager before allowing it to run, blocking pre-OS malware. Required for Windows 11. Leave enabled unless you're installing certain Linux distros without signed bootloaders.

TPM 2.0 / fTPM / PTT — Windows 11 requirement

A security chip that stores BitLocker keys, Windows Hello credentials and platform attestation data in hardware. Required for Windows 11. On AMD it's called fTPM (firmware TPM) and lives in the CPU; on Intel it's PTT (Platform Trust Technology). Both just need to be enabled in BIOS — no physical chip required.

Boot order — which drive loads first

If you have multiple drives, set the one with Windows installed as boot priority #1. After a fresh Windows install, you may need to move Windows Boot Manager to the top of the list manually.

Fan curves — quiet build or thermal headroom

UEFI lets you set custom fan response per temperature point. The defaults are usually fine, but pulling CPU fan ramp-up from 50°C to 60°C dramatically reduces noise during idle and light workloads with no real thermal cost.

CSM — leave it off

CSM (Compatibility Support Module) emulates legacy BIOS for very old operating systems or MBR-formatted drives. Leave it disabled — Secure Boot and Windows 11 both require it off, and there's no modern reason to enable it.

Updating firmware — when and how

There are three legitimate reasons to update BIOS:

• New CPU support. A board that shipped in 2024 may need a BIOS update to recognise a CPU released in 2026 (e.g. AM5 boards needing newer AGESA for Ryzen 9000-series).
• Specific bug fix. The changelog mentions a bug that's actively affecting you — random reboots, USB instability, memory training failure.
• Security patch. Rare but occasional — Intel ME or AMD PSP vulnerabilities sometimes warrant a firmware update.

Otherwise, leave the firmware alone. Each manufacturer offers an in-BIOS update tool: EZ Flash (ASUS), Q-Flash (Gigabyte), M-Flash (MSI), Instant Flash (ASRock). Download the BIOS file from the manufacturer's site for your exact model, copy it to a FAT32-formatted USB stick, enter BIOS and run the flash utility.

Do not: update via Windows utilities (more failure-prone), update from an unstable Eskom cycle without a UPS, or "downgrade" to an older BIOS unless explicitly supported.

BIOS Flashback & Dual BIOS — the safety nets

Two motherboard-level recovery features have made firmware updates dramatically less scary in the last five years:

BIOS Flashback / Q-Flash Plus / Flash BIOS Button

A dedicated button on the rear I/O panel (sometimes also requiring a specific USB port) that flashes a new BIOS file without any CPU, RAM or GPU installed. Plug a FAT32 USB stick with the BIOS file (renamed per the motherboard manual) into the labelled port, press the button, and the board flashes itself in 3-5 minutes.

Why it matters: if you bought an AM5 board in 2023 and want to fit a Ryzen 9 9950X3D, the board needs a 2024+ BIOS to recognise the chip — but you can't enter BIOS without a recognised CPU. Flashback solves the chicken-and-egg problem. Most ASUS ROG, Gigabyte Aorus, MSI MEG/MPG and ASRock Taichi boards have this.

Dual BIOS — the backup chip

Many higher-end Gigabyte and ASRock boards include two physical BIOS chips. If the primary BIOS gets corrupted during a failed flash, the board automatically rolls back to the backup chip. Gigabyte's "Dual BIOS" and ASRock's "Backup BIOS" are the most common implementations.

Common BIOS mistakes

Updating BIOS for no reason. The boards we see bricked are almost universally being updated chasing version numbers, not solving a real problem. Read the changelog. If nothing in it affects you, leave it.

Not enabling XMP/EXPO after a build. Buying 6000 MT/s DDR5 and running it at 4800 MT/s default. A single BIOS visit fixes it. We see this on roughly 1 in 3 self-built PCs brought in for "RAM seems slow".

Disabling Secure Boot or TPM to "fix something". Windows 11 will complain or refuse to install. Almost no real problem is solved by turning these off; many are caused by it.

Resetting BIOS to defaults during troubleshooting and forgetting to re-enable XMP. Memory drops back to 4800 MT/s; performance feels worse; user blames the troubleshooting step. Re-enable XMP/EXPO after any defaults reset.

Flashing the wrong BIOS file. ASUS ROG Strix B650-A and ASUS ROG Strix B650-A WIFI are different boards with different files. Verify the exact model — printed on the box and on the board near the chipset.

Key takeaways

1. BIOS / UEFI is the firmware that runs before Windows — POST, hardware init, then hand-off to the OS.
2. UEFI is the modern version (2015+). Faster, mouse-driven, supports drives over 2.2 TB. Most people still say "BIOS".
3. Tap DEL or F2 at POST to enter. Tap repeatedly — Windows Fast Boot makes the window short.
4. The settings that actually matter: XMP/EXPO, Secure Boot, TPM 2.0, boot order, fan curves. Five minutes total.
5. Don't update firmware unless you have a specific reason. Failed flashes brick boards — UPS or Eskom-free window only.

Frequently asked questions