PC - Overclocking, benchmarks and water cooling

Why would you want to overclock your PC?

If your a petrolhead (gas head?) you will be laughing now. You can never have enough power, processing power that is. So you have had your computer for a while and it has started to feel a little drab and reluctant. Of course there may be many reasons for this, especially for Windows users. If you bought an off-the-shelf HP, Dell or whatever the chances are that the BIOS, or UEFI does not lend itself to changing many settings. However if your machine does, or you built it yourself, or the word gaming appears on it then there is a chance that you can overdrive your CPU, Graphics card and memory too.

How is this possible?

When processors and all silicon chips are made they are made as a huge (relatively) wafer of silicon. Now it is impossible for the purity of Silicon to be 100% due to impurities and imperfections in the manufacturing process. This means that not all CPUs or whatever you are making will have exactly the same performance. So, they draw a line and say all our CPUs will clock at 3.3 Ghz. In practice some will be superior and the inferior ones are either made to perform at slower clock speeds or discarded. So some can be overclocked or made to run faster (subject to motherboard, adequate cooling and PSU control, see below).

My old CPU heatsink and fan

How fast can I clock my CPU then?

OK, the main factors are the frontside bus speed, the CPU multiplier and the CPU voltage. Most motherboards will not let you change these and one of the great advantages of building your own PC is that the manufacturer often will have a selling feature of overclockable or CPU tweaks in the BIOS/UEFI (I will just say BIOS from now on) settings.

Pictures of my BIOS/EUFI setttings

Of course yours maybe very different, refer to your motherboard manual or obtain info from the manufacturers website.

My BIOS/UEFI settings

My ASRock motherboard BIOS settings shown above have an OC Tweaker page and allow me to change the CPU mutliplier from Automatic to Manual which opens up a load of other settings. Check your motherboard manual to see if it is possible for you to tweak.

If you change settings and your computer will not start DO NOT PANIC! Most motherboards will reset their BIOS/UEFI to default settings after three unsuccessful boot attempts. This is also why it is important to keep notes of your last settings.

Now my CPU base frequency is 3.3 Ghz with a Turbo mode of 3.6 Ghz and i have been using it on this setting for over 3 years so I know it is stable. Additionally I have a much better cooler than stock.

Overclocking increases the CPU heat quite a bit, so if you have a stock heatsink and fan you will probably not get very far before it overheats. Luckilly most modern CPUs will just reduce the clock speed internally to protect the chip. The reason this is no longer in my PC is because I have gone a step further and water cooled my PC.

Water cooling, is that a good idea?

Well we know that electricity and water do not mix so we have to be really careful. The other advantage of water cooling is that the fans can be runs slower and controlled by the motherboard so they do not run flat out all the time. This was also true of my previous setup which had 5 fans and a fan controller. Noise was the main reason for me upgrading. I managed to buy a water cooling kit that was factory sealed so no messing with liquids thanks.

My new water cooling kit

I am not sponsored by them and paid for it like everyone else. It may not be the best kit but it is the one that I bought. Also its has pretty RGB lighting, so it won me over, more of that in another article.

I added water cooling

So, I have all that.  How do I overclock my PC?

Looking at my BIOS/UEFI settings the max CPU frequency is 6500 Mhz or 6.5 Ghz, that is almost twice my CPU frequency so that is not going to happen. The frontside PCI bus runs at 100 Mhz on all PCs and I am running a multiplier of 33x giving 3.3 Ghz clock speed. The CPU voltage is 1.38750 volts (write all these down or take a photo of yours before you start) and the maximum for my CPU is 1.55 Volts.

I suggest benchmarking your computer before you start, then you can not only see the improvement (as no two PCs are the same) and know where to stop. Ensure your heatsink and fans are thoroughly cleaned and new heatsink compound applied.

Disclaimer, overclocking produces extra heat and is going beyond the manufacturers specifications. There is a chance of damage to CPU, Graphics card or motherboard. I am not responsible if you damage your equipment. Ensure you have adequate cooling and ventilation before attempting this, and don't be greedy, small steps are very worthwhile.

You will need plenty of time as you need to reboot ever time you change a setting, so get those Windows 10 updates done and get the Coffee on. Take notes every time, it is easy to get lost when changing three or four settings.

If you can change the CPU multiplier from Automatic to Manual then you can begin. Increase the CPU bus by one setting, normally 100 Mhz. Benchmark and run a demanding application while monitoring the CPU temperature (many apps are available but Coretemp is a good one). There is no hard and fast rule as to what is too hot. Generally instability creeps in before anything else, usually within five minutes of running too fast. If you get to this point you can increase the CPU core voltage a little. Now this is going to make the CPU hotter, but they tend to run lower voltages to work with stock heatsinks and if you have a better one can increase the voltage a step or two.

Use PSensor in Linux to check temperatures

At any stage if you get no improvement of stability, back the voltage off and the CPU bus speed. Do not run it any longer than neccesary in instability.

So, how fast did it go?

Well I did a little research beforehand and found that my AMD A8-7650 (3.3 Ghz) is capable of being clocked to 4.3 Ghz, but after a few tests I found that anything over 4.1 Ghz was either unstable or just plain slower than it was at 4 Ghz. This could be due to peripheral components and indeed I changed my graphics card as it was overheating even at stock speeds so I am now running a ASUS GTX750Ti that I acquired secondhand. I also had to change the case as the watercooler would not fit the existing one.  But I ran the benchmarks again just for this article to give a true representation.

Final settings

My final settings

I used Geekbench 5 for Linux Mint and Cinebench 15 for Windows 10 as later versions do not allow OpenGL (Graphics) testing.

So my result in Geekbench (click to download)  in Linux Mint are https://browser.geekbench.com/user/290854 and in Windows 10 in Cinebench (click to download)

Geekbench comparison at different settings

Cinebench 15 OpenGL test

Cinebench 15 CPU test

A very worthwhile improvement. I have been furloughed and using this setup for over a month and have seen very worthwhile improvements, especially when rendering videos.


You can download my original benchmarks at Google Drive, they where done in Linux Mint 19.3 Tricia, Cinnamon desktop, AMD A8-7650K, 16Gb ram 1600 Mhz clocked to 2133 Mhz, Asus/Nvidia GeForce GTX 750 Ti.

My system Info

So please try with planning and caution and you will not be dissapointed!
Let me know how you got on and post your benchmarks