What BIOS is and why you might need to look at it

BIOS (Basic Input/Output System) is the software that runs before your operating system starts up. It controls how your hardware talks to Windows or macOS, and it handles things like boot order, fan speed, and power settings. Most people never need to open BIOS, but if your computer is running slowly, overheating, or not recognizing a new drive, checking BIOS settings can help you understand what is happening.

You access BIOS by restarting your computer and pressing a specific key during startup — usually Delete, F2, F10, or F12, depending on your manufacturer. The exact key appears on your screen for a few seconds when you first turn on the machine. If you miss it, restart and watch more carefully, or look up your computer model online.

BIOS looks different from Windows or macOS. It is a text-based menu with no mouse support — you navigate using arrow keys and Enter. The settings inside are technical, and changing the wrong one can prevent your computer from starting. This guide shows you how to look without breaking anything.

Key Takeaways

  • You enter BIOS by restarting your computer and pressing Delete, F2, F10, or F12 during the startup screen, before Windows or macOS loads.
  • BIOS controls hardware settings like boot order, fan speed, and whether your computer recognizes new drives — not the same as settings inside Windows or macOS.
  • You navigate BIOS using arrow keys and Enter only; there is no mouse, and the menus are text-based and technical.
  • Most BIOS screens have a help key (usually F1) that explains what each setting does, and you can exit without saving changes if you are just looking.
  • If your computer is slow or not recognizing hardware, checking BIOS can show whether the problem is in the hardware layer or in Windows itself.

How to enter BIOS on Windows computers

Restart your computer completely. As soon as the screen goes black and before any logos appear, start pressing the correct key repeatedly — do not hold it down, tap it over and over. The key you need depends on your computer maker: Dell and Lenovo usually use F2, HP and Compaq use F10, ASUS uses Delete, and some older machines use F12. If you are not sure, watch the startup screen carefully — many computers display "Press [key] to enter Setup" for a few seconds.

If you miss the window, let the computer finish booting into Windows, then restart and try again. There is no penalty for missing it. Once you press the right key, the screen will change to a blue or gray menu with white text. You are now in BIOS.

Some newer computers use UEFI instead of traditional BIOS, but the process is the same — restart, press the key, and you will see a menu. UEFI menus sometimes have a mouse pointer, but keyboard navigation still works.

How to enter BIOS on Mac computers

Shut down your Mac completely. Turn it back on and when ready hold down Command + Option + P + R all together until you hear the startup sound twice, or until the Apple logo appears and disappears twice. This resets the NVRAM (the Mac equivalent of BIOS settings) and shows you a recovery screen.

If you want to see the actual firmware settings rather than reset them, restart and hold Command + Option + O + F instead. This opens Open Firmware, which is the Mac equivalent of BIOS. The screen will show a command prompt with a ok prompt. Type printenv and press Enter to see your current settings. This is read-only — you are just looking, not changing anything.

Most Mac users never need to touch firmware settings. If your Mac is running slowly, the problem is almost always in macOS itself, not in the firmware layer. Check Activity Monitor (in Applications > Utilities) first.

What to look for in BIOS without making changes

Once you are in BIOS, look for these sections using the arrow keys to navigate. Do not press Enter on anything yet — just read:

  • System Information or Main: Shows your CPU model, RAM amount, and hard drive size. If your computer says it has 8 GB of RAM but you installed 16 GB, BIOS will show the truth — if it still says 8 GB, the new RAM is not seated correctly.
  • Boot Order or Boot: Lists which drives your computer checks first when starting up. If you recently added a new drive and Windows is not seeing it, check whether BIOS recognizes it here.
  • Hardware Monitor or Status: Shows temperatures for your CPU and hard drive, and fan speeds. If your computer is overheating, this tells you whether the fans are actually running.
  • Integrated Peripherals or Onboard Devices: Shows whether built-in components like USB ports, audio, or network are turned on or off. If a USB port stopped working, it might be disabled here.

Write down or take a photo of anything that looks wrong. Do not change anything yet — just gather information. When you are done looking, press Escape or look for an Exit option. Choose "Exit Without Saving" so nothing changes.

Common BIOS settings that affect performance

If you found something that looks like a problem, here are the settings most likely to slow down your computer or cause hardware issues:

Fan speed set to Silent or Low: If your CPU temperature is above 80°C (176°F) and the fan speed is below 50%, your computer is throttling itself to avoid overheating. This makes it run slower. Changing this to Auto usually fixes it, but only if the fan is actually working — if the fan is broken, changing BIOS will not help.

Virtualization disabled: Some programs (like Docker or virtual machines) need this turned on. If you use these programs and they are slow or will not start, look for a setting called VT-x, AMD-V, or Virtualization Technology and turn it on.

XMP or DOCP disabled: If you have fast RAM, BIOS might be running it at slower speeds by default. Enabling XMP (Intel) or DOCP (AMD) makes RAM run at its rated speed. This is safe and can improve performance noticeably.

find Boot turned off: If you see this disabled and you are not dual-booting Linux, turn it back on. It does not affect speed, but it protects against some malware.

When to ask for help before changing BIOS

BIOS changes can prevent your computer from starting if you change the wrong thing. Before you modify any setting, take a photo of the current state, write down the exact name of the setting, and search for "[your computer model] BIOS [setting name]" online. Look for official documentation from the manufacturer, not random forum posts.

If you change something and your computer will not start, restart and enter BIOS again, then look for a "Load Defaults" or "Reset to Factory Settings" option. This undoes your changes. If you cannot get back into BIOS, your computer may need a CMOS battery reset — search for your model and "CMOS battery" to find the exact steps.

If you are not confident, take your computer to a local repair shop and show them the photo of the BIOS screen. They can tell you in five minutes whether the problem is in BIOS or somewhere else, and whether it is safe to change.

How BIOS differs from Windows and macOS settings

BIOS runs before your operating system loads, so it controls hardware-level things that Windows and macOS cannot touch. If you change a setting in Windows Settings or System Preferences, it does not affect BIOS, and vice versa. This is why a slow computer might have normal Windows settings but a BIOS problem — the two layers are separate.

For example, if your hard drive is running slowly, Windows Disk Management might show it is healthy, but BIOS might show it is overheating or running in a slower mode. Conversely, if BIOS shows everything normal but Windows is slow, the problem is in Windows itself — a virus, a full drive, or too many startup programs.

This is why checking BIOS is useful: it tells you which layer the problem is in. If BIOS looks normal, you know to focus on Windows or macOS. If BIOS shows a problem, you know the hardware itself needs attention.

Frequently Asked Questions

What if I cannot find the key to enter BIOS?

Search online for "[your computer brand and model] enter BIOS" or "[your computer brand and model] setup key". The brand is usually printed on the case or shown on the startup screen. If you have a custom-built PC, the key depends on the motherboard manufacturer — look for a sticker on the motherboard itself or check the manual that came with it.

Can I damage my computer by looking at BIOS without changing anything?

No. Reading BIOS settings causes no harm. The risk only happens if you change a setting and save it. If you are just navigating and looking, you cannot break anything. Always choose "Exit Without Saving" when you are done.

My BIOS shows a temperature of 95°C. Is that a problem?

Yes, that is too hot. Your computer is probably throttling itself to cool down, which makes it slow. Check whether the fan speed is running at 100%, and whether dust is blocking the vents. If the fan is running full speed and the computer is still that hot, the thermal paste between the CPU and cooler may have dried out — this usually requires professional service.

I see a setting called "Fast Boot" or "Quick Boot". Should I turn it on?

Turning it on makes your computer start faster by skipping some hardware checks. It is usually safe, but if you have an older drive or unstable hardware, it can cause problems. Try it and see if your computer still starts reliably. If it does not, turn it back off.

Does BIOS affect how fast my internet is?

Not directly. BIOS controls the network card itself, but not the speed of your connection. If your internet is slow, the problem is your internet service provider, your router, or something in Windows — not BIOS. Check your BIOS only if the network card is not showing up in Windows at all.