As I said before, there are certain inherent risks to overclocking your GPU, so proceed with a level of caution befitting tweaking an expensive bit of electronics. That said, in all my years breaking hardware, it’s never been down to overenthusiastically twisting the nuts off my graphics cards…
Step 1: Know your limits
The first thing you want to do is know where you’re starting from. As a control method it’s worth getting an accurate measure of your card’s current performance. To do so, I recommend downloading some free benchmarking and analytics software.
First off, grab the Heaven 4.0 benchmark. That will give you a platform-agnostic take on your GPU’s performance. It also runs happily in a window on the desktop, which is immensely handy, and will stress your card to make sure it’s all stable.
My personal favourite GPU tweaking tool for Nvidia is EVGA’s PrecisionX software. You’ll need to create a free account to download it from their site, but there are alternatives, such as MSI's Afterburner, if you’re not comfortable with that. PrecisionX also has a handy hardware monitoring window you can pull out which gives you a great bead on how much GPU is being used and the temperature of your card.
With AMD cards, you don't need to download any special software. You can use the Overdrive feature in the Performance tab of the Catalyst Control Centre. Overclocking with Catalyst is a similar basic process to the one I’m going to outline with the EVGA tool, and AMD's graphical interface makes overclocking extremely user friendly.
Once downloaded and installed, boot up PrecisionX to pull in the monitoring data from your graphics card.
Then run Heaven 4.0 in fullscreen at your native res and the highest settings with 4x AA to really push the GPU. You can run the benchmark by pressing F9.
Once that’s done, note down the minimum and average frame rates, quit the application and then note down the maximum frequency your GPU clocked to and the maximum temperature too.
This gives you your baseline performance.
Step 2: Go easy
To get the most out of your graphics card, your best bet is to adjust both the memory clocks as well as the GPU clockspeed. PrecisionX will allow you to do both, but from the outset you want to raise the power limits to 100% to allow full access to the GPU’s power.
Before you start tweaking, boot up Heaven again, but this time run it in a window on your desktop so you can see the looping demo as well as have access to the overclocking controls and the hardware monitor.
Now you can start the overclocking.
Starting with the memory, shift the slider to the right in small, 5-10MHz increments. This will allow you to hopefully see initial instabilities in the VRAM before you fully crash the machine. Moving up slowly like this will give you the best chance of avoiding frying your card too.
After every 10MHz step carefully check the Heaven window for artefacts. You’ll know when your memory is starting to fail as you’ll notice large blocks of solid colours or stars appear on-screen.
When you see those happen, dial back the settings a couple of notches and check the Heaven window again. Keep going backwards until you no longer see the signs of memory strain and you’ve found the limits of your video memory.
Now take a note of the frequency and drop it back down to the default memory clockspeed again.
Step 3: Chip clocking time!
Now we can start overclocking the GPU itself. You’re unlikely to be able to get as much extra speed out of the GPU as you were able to with the memory, but you’re also likely to get a bigger performance boost from tweaking the actual chip than the VRAM.
Follow the exact same method with the GPU slider as with the memory—move upwards in small increments until you start to see some instability in the Heaven window.
This time, though, you are looking for different artifacts in the benchmark display. Instead of stars or blocks of colour you need to keep an eye out for random, multi-coloured pixel-sized dots around the screen. GPU instability might also appear in the form of coloured flashes on-screen. These are the sure signs that your graphics chip is suffering.
As well as artifacts, it’s worth keeping an eye out for the temperature of your GPU in the hardware monitor window. You really want to make sure you can keep your temperature below 90ºC, otherwise you’re likely to start to see throttling, or severely shorten the life of your beloved graphics card. I'd recommend trying to keep the graphics temperature hovering in the 70-79ºC zone.
Again, when you start to see GPU artifacts, drop the GPU clock back until the Heaven window runs normally again. This then is the maximum frequency you’ll be able to achieve with this basic level of overclocking.
If you're using AMD's Catalyst Control Center, follow the same process as above. The interface you're using will look slightly different. Use the memory clock settings slider to adjust the memory speed, and the GPU clock settings box to slowly tick up the GPU speed. Remember, as mentioned above, you'll initially want to crank your power limit settings as high as they can go.
Step 4: Combination therapy
Once you’ve found the limits of both your chip and the video memory attached to it you can combine the two clockspeeds. In your overclocking application push the GPU and memory clock sliders up to your discovered maximums, hit apply and check your Heaven window.
Don’t be disappointed here if your machine crashes or you discover more artifacting in your test window. Pushing up the speeds of both memory and GPU at the same time puts more stress on the card as a whole.
The type of artifacting, as described above, should tell you which component needs dialing back. If you're not sure what the problem is, just set your overclock to 10MHz lower on both memory and GPU when you restart. Keep dropping your overclock by small increments until you get a stable display from Heaven.
Now, close down the Heaven window and restart the application in fullscreen at your monitor’s native resolution. Once the application is running hit F9 and it will start the benchmarking run again. This will both allow you to test if your overclock is stable and give you an immediate measure of just how much extra performance you’ve got out of your graphics card.
Step 5: Stress test
If your PC manages to get through a benchmarking run of Heaven that’s great, but it’s probably worth leaving the software open in fullscreen, running through the loop, for another twenty minutes or so.
That will allow you to really stress test your overclock and make sure it wont fall over in the middle of a tough gaming session. You can also use GPU intensive games, like Metro: Last Light with its tessellated character models, to stress your overclock in a real gaming environment. This is also a good way to see how hot your graphics card will get after extended play time.
Should your GPU not make it through the stress test—whether your whole machine crashes or the display adapter stops working—then simply reboot your system and set the overclock slightly lower again and run through the tests.
This patient, methodical approach should allow you to minimise the stress on your components and ensure you are as unlikely as possible to irrevocably brick your expensive hardware.
Once you’re completely happy with your overclock, it’s time to set it in stone. Your chosen overclocking application will allow you the option to set the new GPU and memory frequencies as Windows starts.
On PrecisionX it’s a simple checkbox and you’re good to go.
One final thing to remember: don't be too down-hearted if you don’t manage to get a huge boost in performance out of your now-overclocked graphics card. You’re never going to get an R9 270X running like a GTX Titan, but what you will be doing is improving the smoothness of your gaming experience.
Even a few extra FPS in a games can make the difference between unplayable and playable, or the ability to turn on that extra bit of post-processing.
You should also, hopefully, be closing the delta between the minimum frame rate and the average frame rate. This is the real key to smooth gaming.
And that’s it—you’re now an overclocker!
What I’ve outlined here is the most basic form of overclocking—if you want to go further you can replace the cooler on your graphics card or start indulging in the arcane art of voltage tweaking.
I’ve chosen to avoid that in this basic guide, as messing with the power going into your GPU raises the chances of something nasty happening to your hardware.
And if a bit of overclocking just convinces you that it's time for a newer and better card, check out or list of the best graphics cards currently available.