If you're anything like me, you really only touch the BIOS if you've just put together a new system, or you're upgrading parts to an existing one. A quick tour of changing a handful of the usual settings just to get up and running, and that's it. However, lurking in the depths of your motherboard's firmware could be remnants of old troubleshooting steps, forgotten toggles, or poor default settings that are sneakily making your PC worse, and it's a good idea to go through and tie up these BIOS loose-ends.

CSM and Legacy Boot enabled

Blocks other important settings from being enabled

One of the most common BIOS settings that is toyed with in the troubleshooting process is Legacy Boot and CSM. These are commonly toggled on and off to try and get Linux or an older OS like Windows 7 installed on a modern system, if you're having boot device issues, or even in cases of a failed BIOS update.

CSM stands for Compatibility Support Module, and leaving it on can block other useful settings from being enabled, namely Resizable BAR, which is very important for getting the best out of modern GPUs. If you're on an older system, or you're running a legacy OS that requires Legacy Boot, you might be leaving performance on the table. The right move is to switch the motherboard to UEFI only, convert your boot drive to GPT if it is still MBR, then enable Above 4G Decoding and Resizable BAR. Many GPU control panels show a simple on or off indicator for Resizable BAR, which makes verification easy. In games, expect a small uplift that costs nothing, with the occasional title showing a bigger gain.

“Performance Enhancement” auto-overrides

A little bit of manual tuning goes a long way

Many motherboards ship with auto performance enhancers that quietly increase power limits, and on Intel systems, this often shows up as Multi-Core Enhancement, which forces high turbo clocks across many cores by raising PL1 and PL2. On AMD, some boards set very loose Precision Boost Overdrive limits.

The result of this (if you have adequate cooling) is more performance, but it is a rather ham-fisted way to go about it. If you have a budget cooler, short bursts might look fine, then the system sinks as it bumps into temperature or VRM limits. A smarter approach is to start with stock settings. Set Intel power to Intel Default or manually configure reasonable power limits near spec. On Ryzen systems, enable PBO conservatively and focus on Curve Optimizer with a negative value to reduce voltage and heat while keeping boost. You can judge success with a quick Cinebench run, OCCT loop or Prime95 stress test while logging clocks and temperatures. The goal is equal or better performance with lower heat and no throttling flags.

Stock fan curves

Even the pre-made curves shouldn't be used

If tuning the CPU manually is a 4/10 on the effort scale, tuning the fan curve of your system is barely a 2. The stock settings that your motherboard ships with will likely be enough to cool your system thoroughly in most scenarios, but let's say you want to quiet your fans or lower temperatures further. You might be tempted to try the "turbo" or "silent" profiles that are available as a turnkey solution, but in reality, these curves are hardly ever effective, and this one-size-fits-all approach often makes things louder or warmer than they need to be.

Spending the time tuning your fan curves in the BIOS can not only make things cooler and quieter, but it also ensures that they save properly. There are software solutions in your OS that can control your system fans, but they're not applied at boot, and any issues with the software means your curves may not be applied properly.

Leaving XMP/EXPO off

It can't be said enough

Your RAM carries a few different speed and timing profiles with them. The slow, universal profile is called JEDEC, and it is what every kit falls back to for maximum compatibility. The faster, vendor-tested profiles are XMP on Intel platforms and EXPO on AMD. If you never turn these on, your kit runs below the speed you paid for, and with looser timings to boot. If you've done a BIOS update or a CMOS clear in the process of troubleshooting another issue, it's very likely that XMP/EXPO has been turned off.

Having it toggled off means less bandwidth, higher latency, and a real hit to gaming minimums and everyday responsiveness. APUs and any system that leans on integrated graphics feel it even more because they share system memory. The fix is to enable XMP or EXPO in the BIOS, and you should see immediate results. You can confirm which settings are currently enabled by checking memory frequency in Task Manager or CPU-Z, and by running a quick game benchmark to validate performance.

Your BIOS holds the keys to more performance

Tuning these BIOS blind spots provides free performance and quieter operation. Enable the right features and verify each change with a quick benchmark and a temperature log. Save a known good profile before you start, and you will finish with a PC that feels faster, boots cleaner, and stays cooler without feeling like you need to rush into an upgrade.