When building a new PC, the default BIOS settings aren’t exactly optimized; you need to spend a few minutes to make them so. Most PC builders know about BIOS settings. However, most PC builders only ever touch the most common BIOS settings like XMP/EXPO, fan curves, and resizable BAR. They forget about some advanced or lesser-known settings that can play a major role in the functioning of their PC. From reducing power consumption and improving performance to ensuring reliable operation, these obscure BIOS settings are indispensable to making the most of your PC.

Disable unused peripherals

Why waste power and resources?

You might not be using every port and slot on your motherboard, but that doesn’t mean your PC isn’t initializing and sending power to each of them whenever you turn it on. SATA ports, Wi-Fi adapters, and integrated graphics & audio are some of the most common ports and onboard devices that people never use, but they’re often left enabled. There’s no harm in doing so, but disabling them can have some advantages, such as increasing power efficiency, freeing up address space for other things, minimizing hardware conflicts, and speeding up the boot process.

Suppose you’re not using the onboard graphics on your PC. To disable it, you can head into the BIOS/UEFI, find the section for “Integrated Peripherals” or something similar that displays options like “Onboard Graphics”, “iGPU”, or “Integrated Graphics Device”. Disabling it will ensure you aren’t wasting small amounts of power on something you never use, and you’ll not have to maintain device drivers for it either. You could also disable onboard audio if you only use USB speakers. Disabling these unused controllers and devices may not boost performance, but they can simplify your boot process and prevent unnecessary Windows shenanigans.

CPU C-states

It’s not just for idle power reduction

Your CPU’s C-states represent various sleep states, each progressively more aggressive in shutting down parts of your processor when unused to reduce idle power consumption. By default, your CPU’s C-state behavior is set to “Auto”, leaving the task of balancing energy efficiency and performance to your PC. Depending on the current load, your CPU will keep switching between various C-states to optimize power consumption. These C-states usually range from C0 to C7 — the higher the number, the more aggressive the sleep behavior. For instance, a CPU in C6 might only sip fractions of a watt, keeping awake the bare minimum of CPU logic.

While the average user doesn’t care about tweaking C-states, doing so can actually improve performance and reliability, even in gaming. Many users report more consistent performance after disabling C-states entirely, meaning the CPU isn’t allowed to put its internals to sleep, ensuring it is “always at 100%”. At the same time, other users report increased stability by *enabling *C-states, with some Ryzen 7 9800X3D users reporting higher performance. The internet isn’t exactly united on the data, but it’s worth checking your BIOS/UEFI to ensure your C-state settings aren’t set too high or low. Home lab users might want to take advantage of all the C-states to ensure minimal idle power consumption, while gamers and overclockers could benefit from disabling C-states entirely.

ErP mode

Comprehensive power management

ErP, or Energy-related Products, is another one of the features in your BIOS that reduce power consumption, both when your PC is on and off. This setting came about as a result of an EU directive, and every motherboard sold since 2009 will have this feature somewhere in your BIOS, likely in a section about power management. If you live outside the EU, this feature is probably turned off by default, so you’ll need to enter the BIOS/UEFI to enable it. You might wonder what it does, though. Enabling ErP activates several power-saving features, like optimizing the power sent to unused devices and enabling the low-power C-states that I mentioned earlier.

ErP isn’t terribly important if you’ve already disabled unused peripherals and controllers, and enabled C-states, but it can act as an umbrella setting for users who haven’t messed around with the other two settings. The ErP settings in your BIOS will also come in handy if you want to disable power for your USB ports when your PC is in sleep mode. This can be useful for people who don’t want to accidentally wake up their PC with the keyboard or mouse. If you actively want to do that, however, then leave the setting related to USB standby power untouched.

Compatibility Support Module

Don’t mess with it unless you know what you’re doing

You may not have heard of the Compatibility Support Module (CSM) if you have a relatively modern PC with UEFI firmware. In fact, even those running BIOS in legacy mode might not discover it until they try to enable Resizable BAR (ReBAR) for enhanced performance. CSM is a bridge between the newer UEFI firmware and older operating systems and devices to ensure compatibility. It’s essential to allow your PC to boot your OS installed on an MBR-formatted disk. Although the modern GPT formatting standard has been around for years, it’s possible that your Windows 10 installation exists on an MBR disk.

While most Windows 11 users will probably never need to know about CSM, those on MBR-formatted drives can run into problems when trying to enable ReBAR in the BIOS. The thing is, ReBAR requires “Above 4G decoding” to be turned on, and this setting doesn’t support the legacy BIOS mode. If you turn on these two settings on a system running an OS with legacy BIOS support, the UEFI firmware will automatically disable CSM, and the system will fail to boot. The so-called “UEFI-only” mode will no longer recognize your MBR-formatted disk with your OS, leading to a boot failure. Unless you revert the settings or convert your SSD from MBR to GPT to allow the UEFI-only mode to run, you’ll be stuck with an unresponsive PC.

Multicore Enhancement on Intel CPUs

You probably don’t need it

Multicore Enhancement (MCE) is an Intel-specific BIOS setting that enables each of the CPU cores to run at the maximum boost clock simultaneously, instead of the usual behavior of a few cores boosting at a time. This setting can be beneficial to those chasing high multicore scores and have the cooling hardware that can handle the additional heat output. MCE may appear to be a win-win to most people, but it’s actually something that you can safely avoid, saving yourself the headache of unstable operation and needlessly high CPU temperatures.

Most users do not need all their cores running at maximum frequency all the time. Gamers will see minimal benefits, and the potential downside of excessively high temps and crashes makes this setting mostly unnecessary, unless you really need the extra power for multicore workloads. Most people are better off undervolting their Intel CPU and/or manually overclocking it for better results. You’ll at least have control over how far you want to take your chip, and you can modify the power and voltage settings according to your cooling setup’s capabilities.

Knowing which BIOS settings you really need is key

Although your BIOS/UEFI will have countless settings you could tweak, knowing what’s actually relevant will make your life a lot easier. Not every performance-enhancing feature really benefits every use case, and some settings are best left disabled to ensure stable operation. Unless you’re an enthusiast and know what you’re after, you can leave features like MCE disabled. Many of the settings listed above aren’t widely known, but they’re still worth knowing about.