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How to Overclock a CPU in the BIOS

Step by Step Guide to Overclocking Directly in the Motherboard's BIOS

Step 1: Download CPU Benchmarking Software 

You’ll need to download a stress-test/benchmarking program and a hardware/temperature monitoring program to test and check your overclock for stability, as well as comparing your pre and post performance. CineBench R15 is a good, free stress-test program that includes a CPU test that’s really popular across the enthusiast community (search google for the download). Geekbench is another good one. 

Prime95 is yet another popular choice and will really push your chip to its limit and utilizes all cores. Be careful with this program because it’s very stressful to your system and therefore has the (rare) potential to really overheat your CPU and/or damage it if used improperly. Don’t run it for too long without keeping an eye on temps.

Download 1, 2 or all 3 of these programs and run the automated tests (in Prime you should do a “blend” test), making sure to close any background applications first so nothing interferes with the tests (and do the same when you run it again during/after your overclock).

Step 2: Download Monitoring Software

As for temperature monitoring, which is an important of overclocking, some of the best, most popular free tools for that right now are HWMonitor, Open Hardware Monitor, HWInfo64, CPU-Z, and RealTemp. 

Go ahead and download one of these programs, or get more than one if you want to either compare which you prefer, or to cross-check hardware readings across multiple programs which is the ideal way to do things if you want to be as accurate as possible. If in doubt just get HWMonitor as it’s pretty standard and works well.

See Also: Recommended Software for a New Gaming PC

Step 3: Refer to Manual & Locate CMOS

Grab your motherboard manual and use it to find where the CMOS reset button is on your motherboard if you have no clue where it is. You may not need to use this button, but if things go bad during your overclock you’ll need it so you might as well become accustomed to where it is and ensure you can reach it within your case. 

Instead of pushing this button if things go bad, you could remove and reinstall the actual CMOS battery which would also reset your board back to the default. Your motherboard manual may also explain some of the BIOS settings related to overclocking, so have a read of it now while you’re at it to get more accustomed.

Step 4: Should You Update Your BIOS?

Depending on whom you ask, before overclocking you will either want to update your BIOS or completely forget about it. Updating your BIOS can cause implications if you’re not careful, so I would check which version you’re currently running (it’ll show on-screen somewhere) and check that against the latest manufacturer’s version on their official website. 

You want to try and find any information regarding whether there are BIOS updates that have helped overclocking compatibility/capability in some way that could affect you. It’s ultimately your call as to whether you update or not; personally I would give it a miss because there is the risk of it causing more problems than it solves, unless you know that updating will help your system in some way (solve an issue, help with overclocking, improve performance, etc). Unfortunately, there’s no simple yes or no answer. 

If your BIOS is out of date and you do want to update and are clear about the potential risk, then go ahead and do that now before overclocking. To do so, download the latest BIOS file from the website and extract the .CAP file into a FAT32 formatted USB stick. Plug your USB drive into your PC, restart your system and open the BIOS, head to “Tool” or something like that, and select the BIOS update option somewhere. Select your flash drive and choose the .CAP file.

Step 5: Research Optimal Settings (optional)

One handy thing to do before diving into overclocking and trying to manually find optimal settings for your particular system is to do a little research around for what others have successfully used for your specific chip. 

Whilst you won’t necessarily get the same results as there are a lot of variables at play when it comes to overclocking, even if you do have the exact same specific CPU as another user, it can be helpful to get a general idea of what works well. Check out communities on sites like HWBot, Overclock and Overclockers.

Step 6: Open BIOS Overclocking Settings

Restart your PC and repeatedly press either delete, F8, F12, or whichever key brings up the BIOS for your particular motherboard. Check your motherboard manual for the right key if nothing works. You’ll be brought into the top-level menu, but you need to go deeper into the CPU settings area where you can see things like the multiplier, base clock, core clock, voltage/VCore, etc. This area could named advanced or something else like overclocking settings, clock settings, OC tweaker, extreme settings, etc.

Some motherboards may actually have the overclocking settings hidden away and will need to be unlocked somehow. For example, to access the full spectrum of tweakable CPU settings in some ASUS motherboards you have to set the “Ai Overclock Tuner” to manual and the “EPU Power Saving Mode” to disabled. Again, refer to your particular motherboard’s manual if you get stuck.

Step 7: Increase the Multiplier

Now it’s finally time to overclock. More significant overclocks will require upping the CPU voltage, but first we want to find the maximum stable speed without having to apply extra voltage. Applying more voltage will increase the risk of shortening your CPU’s lifespan or damaging/overheating your hardware, and isn’t a necessary step to get a nice performance boost from a CPU overclock. But it is the only way to truly push your CPU to its limits should you be comfortable with doing that and have the proper cooling in place.

Before increasing the actual multiplier number, look if there is also setting to change how the multiplier is applied. You want this to be set to something like “Sync Across All Cores” or “Manual” instead of “Auto”. This is what you want for simplicity, especially as a beginner. You don’t want to be tweaking each core of your CPU individually. Again, this will vary from motherboard to motherboard, but look for a setting called the Multiplier, which could be called the CPU Ratio. Don’t confuse this with the base or adjusted frequency.

We mentioned this earlier in this module, but let’s refresh: the speed of your CPU, or specifically the clock speed, is calculated by multiplying the base clock speed (BCLK) by a single number called the multiplier. For example, if your CPU has a BCLK of 100Mhz, and the multiplier is set at 35, your CPU clock speed would be 3500 Mhz (or 3.5 GHz). If you then change the multiplier to say 38, your clock speed is now 3.8 GHz. Simple stuff.

So once you’ve found where to change your multiplier in your particular BIOS (you may not have that option and will have to directly increase or manually input the actual clock speed instead) then take a mental note of it just in case (or write it down if you have bad memory!). If at anytime during your overclock things go wrong and you want to revert back to the default settings, your BIOS should have an option to do exactly that. 

Otherwise, you could always reset the CMOS jumper on your motherboard if things go bad. Some older motherboards might require you to actually physically remove and then reseat the CMOS battery instead. As always, check your motherboard manual if you’re unsure.

To start off with, you should be fine with increasing it by 5, and then if that speed comes back as stable in your testing then you can continue on to increase it by a smaller amount such as 1-2 at a time.

So, go ahead and increase that multiplier by 5, or less if you don’t feel comfortable with that kind of initial jump. To change the value you may have to use the arrow keys on your keyboard, or you might have to actually enter in the number value you want. Now it’s time to move onto testing your new speed for stability. 

Step 8: Test Your Overclock

Restart your PC, run your stress-testing software such as CineBench R15 or Prime95, and open up your monitoring software such as HWMonitor. Now you want to run CineBench R15 or Prime95 (or another) to check whether your new speed is stable as well as monitor your CPU temperature to make sure it’s running at a safe level.

If using CineBench R15, go to File->Advanced and run the full CPU benchmark. If using Prime95, go to Options->Torture Test->Blend Test. These tests will push your CPU to its limit to test if your new clock speed is stable.

While running either test, keep an eye on your CPU temperature in HWMonitor or your monitoring tool of choice. If you go over 75-80 degrees Celcius at any time, you may want to consider turning down your overclock as it may not be safe for your CPU to run that hot under load. 

If either benchmark finishes or runs for 5-10 minutes without freezing, showing a blue screen, or crashing your system, you’re safe to further increase your multiplier and testing again until you find the highest safe/stable speed for your CPU.

Remember that you should probably increase your multiplier by only 1 or 2 at a time after that initial increase of 5, but as mentioned you may want to start with 1-2 instead of 5 anyway (if it makes you feel better).

Keep repeating this process of increasing slowly and testing until your system crashes, freezes or you get a blue screen of doom. If that happens, don’t worry as it’s part of the process, and reboot your PC. 

You basically have two choices after encountering an unstable CPU clock speed:

1. Go back into the BIOS and lower the multiplier back to the last stable setting and be done with your overclock, or
2. Continue down the rabbit hole and try your hand at increasing CPU voltage settings to see if that stabilizes your new CPU speed.

Step 9: Increase the Voltage (optional)

Look for a CPU Voltage/VCore setting in your BIOS that is something like “Vcore Voltage Mode” or something else, and have this set to “manual” or “fixed”. This is the setting to have your voltage fixed, meaning that whether or not your CPU is under load or idle it will still receive the same amount of voltage.

You want to start be increasing the actual voltage setting by a small amount of around 0.025 0.01 V or whatever you’re comfortable with or have researched for your particular chip. Whatever you do, be careful with increasing your voltage and never do so wildly as it’s the most risky setting to tweak when it comes to overclocking any component.

With each small step up in voltage/VCore, you want to test if you can successfully boot, stress-test and maintain stability at the faster multiplier/speed from the previous step. You could bump up the voltage by more at a time, such as 0.05 or higher, but as a first-timer you want to keep it as low as possible unless you know what you’re doing. It really depends on your CPU too and how it reacts to voltage increases.

Once you have successfully pulled off a voltage increase at a new multiplier/speed setting, you can go back and repeat step 10 again and then come back to increasing the voltage slightly again once you reach an unstable new speed. Repeat this until you reach your desired overclock, your temperature gets too high under load, or you’re at 1.4 V or higher. 

Going higher than 1.4 V is possible, but can be very risky, especially if you’re running an air-cooled system only (this is where water-cooling seems super practical all of a sudden). There is also the point where you can’t stabilize a certain CPU speed no matter how much voltage you throw at it, and when that happens you want to lower your speed slightly (0.1GHz etc) and lower the voltage back to the last stable setting for that speed, and then run longer stress-tests to confirm that this is a stable and cool-enough overall speed.

Step 10: Run Thorough Stress-Tests

When you think your system is stable at a speed, voltage, and temperature you’re happy with, your work isn’t done. It’s time to really test your setup to ensure it’s not going to crash under extended load. You should run benchmarks for as long as you feel appropriate, whether that’s a few hours to a full day or even longer, and check CPU temperature readings using your tools. Depends on how thorough you want to be. Oh, and your patience ;)

Prime95’s “Blend” test is super intensive, and if your PC survives that one for extended periods (say, 24 hours) without crashing or reporting errors then you can bet your system is stable. CineBench will work well, too. If your do encounter errors or crashes during this final testing, either decrease the speed or test with slightly higher voltages again until you are stable again (and don’t forget to monitor temps again to stay under 75-ish degrees Celcius under load).

That's all for this overview of BIOS overclocking - be sure to do your homework before undertaking this and make sure you know what you're doing. Good luck.

See Also: How to Overclock an Intel CPU Using XTU (Without BIOS)

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