Introduction
So many users are searching around the net these days looking for advice on how to overclock their new systems but don’t know where to start. To help everyone out, I decided a how-to guide was in order. Searching around forums can be confusing and intimidating. There are so many people willing to give advice, but who can you trust? It’s hard to know, and I’ve seen many users sent on wild goose chases because they are following advice that doesn’t solve or even address their specific problem. I’ve also seen too much trial and error overclocking. What I will attempt to do is create a very simple three step guide to “one-size-fits-all” overclocking.
If you want to continue searching out other opinions, please consider each suggestion with caution. Some will undoubtedly be great, some will not. There is one exception I would make for OC Forums- their “senior members”. These users are the ones with blue user names and blue stars. They have been designated seniors based on their knowledge, experience, credentials, and contributions to the OCF community. While not immune to error, these users generally know their stuff and can be trusted for good advice.
Credentials
So, why should you listen to me? Well I’m not the end-all-be-all of overclocking, and I still learn new things everyday. There are many people around OCF whom I highly regard for their knowledge and experience. Having said that, I do have a bit experience overclocking computers successfully. I’m a member of Team IRONMODS, and if you’d like to know more about the team and our accomplishments, please visit our website. I’m also very active with the OCF benching team where I regularly participate in team events and online competitions with The Raptor Pit.
Methodology
My goal here is for this overclocking guide to be useful for anyone with a newer Intel based system, i3, i5, i7, LGA1156 or LGA1366. With the same basic principles applying to all of them, the basic process doesn’t change whether you are planning to use your system as an everyday system, gaming or if you want to push the limits for a single benchmark.
This guide is also independent of your cooling system. Whether you are using the stock Intel cooler or if you’re pushing to the extreme with liquid nitrogen, the basic steps remain the same. One thing that is far too common is errors in mounting your cooling system, specifically the application of the thermal interface material (TIM). If you don’t have much experience mounting a cooling apparatus, please refer to this excellent guide from Arctic Silver.
Determining methods for finding a stable overclock are highly controversial, and my suggestion is that we agree to disagree. Everyone has their individual definition of a stable system, but when I refer to “stable” in this guide, I am referring to the stability of your selected “stability test.” So for a power user or gamer who wants a reliable system that won’t ever crash due to an overclock pushed too far, you’d need to test with a program that will load all of the cores and threads applicable to your CPU, OCCT and Prime95 are two popular choices. For a benching team member looking to squeeze every last MHz out of their chip for a 7 second SuperPI 1M run on liquid nitrogen cooling, SuperPI 1M would be the ideal test. In my examples below, my verbiage will obviously be geared more towards those running tests like Prime95. Super PI 1M only takes a few seconds to complete, so when I say “run your stability test for five minutes” obviously you will have to tailor that instruction for your individual situation.
So with that in mind, we will attempt to isolate each portion of the system and overclock one piece at a time. This may seem time consuming at first glance, but rest assured this can potentially save you hours of troubleshooting and frustration. So go slow, and follow each step very carefully.
Prerequisites
This guide is written for you if you can get around in your system’s BIOS (basic input/output system). I cannot write this guide to cover the variety of BIOS represented. If you are unfamiliar with your BIOS, search for more information regarding your specific motherboard. Also, do not be afraid to get into your BIOS and have a look around, if you are ever concerned that you may have changed a setting erroneously, you can always load defaults, and start over.
I also need to insert a disclaimer in here somewhere: I am not responsible for any bad things that happen to you or your computer as a result of you listening to my advice, nor is overclockers.com. My goal is for this guide to be a safe overclocking guideline, but the burden for damaged hardware lies on the user performing the overclock! Overclocking can damage hardware, the new 32nm CPUs seem to be particularly fragile. Overclocking will also void your warranties.
Before we do anything, please start by going into your system’s BIOS, and load defaults, then save and exit. Your machine will restart with default BIOS values. Enter the BIOS again and disable all power saving features. These include, but are not limited to; EIST, C1E, and all other C-states. All other settings you can leave on auto for now. Although I would also recommend turning off any start-up slash screens, so that you can view your system’s post behavior. Also, feel free to disable any “integrated peripherals” that will not be used (i.e. NICs, extra PATA/SATA controllers, legacy devices, etc).
If your motherboard fails to post after changing certain settings, you will have to locate and reset the CMOS. Resetting the CMOS restores the BIOS to its factory settings and is a “hard” reset of these settings. Become familiar where the CMOS jumper or button is, you may need to use it a lot. Most of the time, a jumper is located near the battery on the motherboard, most newer motherboards have a button in the same location, many may also have a button on the rear input/output panel for easy access when your motherboard is installed in a case. If you need to reset the CMOS, please power off the system by flipping the switch on your power supply, or unplugging it completely for 10 sec, then activate the CMOS reset jumper/button for 10 sec.
3 Step Guide to Overclock Your Core i3, i5, or i7
Step 1) Bclock Frequency
Isolate the bclock from the CPU
First you need to isolate the bclock and find its stable limit with your chosen cooling. In order to isolate the bclock from the other components, the first thing you need to do is manually force a low multiplier for the CPU. For example; at stock speed, an i5 750 runs on a 133MHz bclock and a x20 multiplier which results in its stock speed of 2660MHz (133×20). Raising the bclock to 200 with the stock x20 multi would result in 4000MHz for the CPU, which you’re not quite ready for yet. If you are shooting for a 200MHz bclock, then a safe choice for now might be a x12 multi, which would result in a CPU speed of 2400MHz if you were successful in reaching your 200MHz target bclock. Doing this isolates the CPU from the bclock so you can focus on only bclock overclocking in this step.
Isolate the bclock from the memory
The fastest rated speed for memory on P55 with an i5 750 (for example) is DDR3-1333, which is a clock speed of 667MHz (dual data rate “DDR” doubles the bandwidth to 1333-like speed). Just like the CPU, the memory receives its clock from the bclock via a multiplier, in this case x5 (133×5=667). This is most often expressed in the BIOS as “2:10″. If you were to overclock the bclock to 200MHz as described before, your memory would be running at 1000MHz (DDR3-2000), and beyond the specs of all but the most extreme memory. To isolate the memory from the bclock, lower the memory multiplier to the lowest setting available, most likely 2:6. If you were to reach your goal of 200MHz bclcok frequency, your memory would only be at 600MHz (DDR3-1200) and well within the capability of all but the worst DDR3 on the market.
Bclock voltages
For this step, there are only two voltages you should play with; CPU VTT, and IOH. IOH is easy, if you are running a single PCIe card (graphics card), give the IOH 1.3V, if you are running more than one PCIe graphics card, give it 1.35V. CPU VTT is the crucial voltage adjustment for achieving high bclock stability. Stock values differ depending on platform and CPU, but as a rule of thumb LGA1366 likes a lot, P55 doesn’t need as much.
So, are you ready to start overclocking? After entering your BIOS and lowering the CPU & MEM multipliers, go to the voltages section and raise your IOH to 1.3-1.35V and your CPU VTT to +0.2V. Then restart your machine and go back into the BIOS, if your system fails to post and return to the BIOS, please re-read the last paragraph in the “prerequisites” section above, and start over. If you still cannot get past this step, post in the forums for some specific help.
After you’ve restarted your system with your manually configured voltages and returned to the BIOS, I always recommend going to the temp/voltage monitoring section and checking the CPU temp. If the temperature seems too high for your cooling, then shut the system down and double check that your cooling system is properly mounted, and making good contact. Moving on, almost all systems should be able to achieve 150MHz bclock stability with stock voltages, so go to the bclock adjustment and change it from 133MHz to 150MHz. Then save and exit and allow the system to reboot. This time, allow the system to boot fully into the operating system.
Testing for highest stable bclock frequency
Once the operating system has fully loaded, start up RealTemp. RealTemp should always be running while checking for stability of an overclocked system to ensure you do not overheat your CPU. RealTemp shows your CPU’s core temperatures real-time, as well as the distance to TJ Max, my advice is to never exceed TJ Max. Now start up CPU-Z, this will allow you to ensure that your overclocked settings have been properly applied, and that you are running at your desired speed. Check both the CPU tab for the expected CPU frequency (should be 1800MHz at this point), and check the memory tab to ensure your memory is running at the proper speed (CPU-Z will show the frequency of the memory, not the DDR3 speed, it should be 450MHz at this point). Now start up you selected test program, for example OCCT or Prime95. Run the test for just a short amount of time, five minutes should be plenty. Then reboot the system and return to the BIOS.
If the test ran without error, raise the bclock by 10MHz, reboot into your OS and run the test again. If the test failed, raise the CPU VTT voltage by a small increment, reboot into your OS and run the test again. You should be able to see where this is going, continue to raise bclock or CPU VTT voltage with a short test after each change, until you meet one of the following criteria:
- You reach your desired bclock and successfully pass your stability test.
- You reach your maximum safe CPU VTT voltage.
- Raising the CPU VTT does not allow for additional stability.
* Note – there is a phenomena known as “bclock holes,” which seem to be less common now, but may still create confusion and frustration during this process. But if you appear to have found your limit at a much lower speed than anticipated, please consider trying a step or two higher before continuing on. A bclock hole causes system instability a particular bclock values, and going past them may allow you to regain stability.
Maximum safe CPU VTT
What is the maximum safe CPU VTT voltage? Depends on a lot of things, but I feel like these are some basic– conservative guidelines. If you’re running the stock Intel heatsink and fan, I would not advise more than +0.2V, if you are running a high end air cooler I would not advise more than +0.3V on LGA1156 platforms, and no more than +0.4V on LGA1366 systems. If you are running a high end custom water loop add another 0.05V to those values, and if you are using extreme forms of cooling then use whatever works best. I’ve used up to 1.70V on an i7 920, and up to 1.55V with my i5 750 with extreme cooling.
Fine tuning
After you have met one of the criteria above, you should have a rough idea of your bclock limit, now it’s time to get a little finer tuned. Next, instead of 10MHz bclock changes, shift to 2MHz changes. Then repeat the steps above and search for one of the three criteria again. Also, ensure you check my note about “bclock holes” above, the same concept can be applied to this fine tuning step as well.
After you have found your highest stable speed to within 2MHz accuracy, lower the bclock by 2MHz and run your test again. This time let it run for a full hour (for those of you testing with Super PI or similar, adjust for your situation). If it passes the test - Congratulations! – you have found your highest stable bclock frequency.
Step 2) Memory Frequency
DDR3 Basics
The next step is to find the limit of your memory. To do this first you need to look at the memories ratings. DDR3 does not typically have a lot of overclocking headroom, so it’s important to start with stock settings. In this example I will use some basic Crucial Ballistix PC3-12800 for my explanations. This memory is rated for DDR3-1600 (800MHz) 8-8-8 24 1T with 1.65V. Enter the BIOS and adjust your memory timings according to the manufactures rating, in this case 8-8-8 24 1T. Now, consider your maximum/desired bclock frequency, 200MHz for example. This memory has a stock speed of 800MHz, so a 2:8 ratio with a bclock of 200MHz would put us right at that stock speed of 800MHz. You could set it and leave it there, but let’s say your maximum/desired bclock is not 200MHz. For example, if you are actually trying to reach 210MHz. If that were the case, the resulting memory frequency would be 840MHz (DDR3-1680). So, similar to finding bclock stability above, we need to work our way up to the desired speed testing along the way.
Testing for highest stable memory frequency
Theoretically we should be able to run for at least an hour with the bclock at 200MHz and the memory multi at 2:8– why? Because we already found out that this bclock speed is 1 hour stable, and we are not overclocking the memory yet.
However, the integrated memory controller (IMC) is powered by the CPU VTT voltage. So under some circumstances, especially with the newer 32nm CPUs, you may not be stable with your memory even at stock speeds due to the overclock imposed on the IMC. This is particularly true if you are running 4 DIMMS (P55/H55/H57), 6 DIMMS (X58), or 4GB DIMMS (P55/H55/H57/X58). If this is the case keep the memory at stock speed, or even try dropping the memory clock multiplier to run at less than stock speed, and increase the CPU VTT voltage until you gain stability. The newer 32nm CPUs seem to have particularly weak IMCs, and often will not run at the higher multipliers even if your memory is perfectly capable.
For testing memory, it is important that you take a break from whatever stability test you’ve been running, and use memtest86+ instead. The easiest way is to download the .iso and burn it to disc. Then configure your BIOS to load from your optical drive before the hard disk drive. When you boot the system with the disc inserted, memtest86+ should start automatically, and immediately begin testing your memory.
But, our goal is to reach 210MHz bclock, which will result in 840MHz memory frequency. In the BIOS, set your bclock to 202MHz, and your memory multi to 2:8, save settings and exit. Allow memtest86+ to load and complete one entire loop. A single loop can vary in length, and can take quite a while if you have a large amount of memory installed. If the test ran without error, press Ctrl-Alt-Delete and enter your BIOS. Raise the bclock by 2MHz and then save and exit. If the test failed, raise the memory voltage by a smallest increment possible, and run the test again. You should be able to see where this is going. Continue to raise bclock or memory voltage until you meet one of the following criteria:
- You reach your desired bclock and successfully pass a single loop of memtest86+.
- You reach your maximum safe memory voltage.
- Raising the memory voltage does not allow for additional stability.
Maximum safe memory voltage
What is the maximum safe memory voltage??? This is determined by two things: first, NEVER INCREASE THE MEMORY VOLTAGE MORE THAN +0.5V OF THE CPU VTT VALUE, second, how much do you enjoy killing your memory? Throughout recent history, memory is probably the easiest component to damage with extra voltage. While there are exceptions, most newer DDR3 memory modules do not need very much voltage to reach their practical limits.
Once you have satisfied one of the three criteria above, drop the bclock down 2MHz from your last stable setting, and see if memtest86+ will run through 2 or 3 loops without error. If you wish to try to push your memory even further at this point, there is one more thing to try, and that is another bump in CPU VTT voltage. This will possibly boost the capabilities of the IMC and give you a little more room to overclock the memory. Otherwise - Congratulations! - you now have a relatively stable bclock frequency and memory frequency.
Step 3) CPU Frequency
Almost there
The last step in this guide is often the first step for users who run into problems and then troubleshoot for days afterward. Leaving it to the last step makes the task much simpler. You now have the following settings locked in; CPU VTT, IOH voltage, memory voltage, memory multiplier, and memory timings. That means when we are looking for our highest CPU frequency, there are only two variables we need to play with: bclock and CPU voltage.
Right now your CPU multiplier should be very low, and your bclock should be quite high. If we move the CPU multiplier up right now, we would undoubtedly become very unstable, and unlikely to post. The idea here is that if your bclock and memory are stable with the current settings, shifting the bclock down should not cause any instability. So, change you bclock to 140MHz, and switch your CPU multi up to its maximum. In our example i5 750, the normal maximum would be x20. Intel’s Turbo feature allows for extra multipliers, and some BIOS will even allow for the higher multipliers to be forced. It will not hurt to use this feature if you desire. So with my example of the i5 750, with some BIOS, I would be able to lock in a multi of x21.
“Load-line calibration”
This actually goes by a few different names, but they are all meant as a means to reduce or prevent v-droop. Most overclockers would advise you to enable this feature; I would only recommend it if you understand what it does. It does typically allow for measurably higher overclocking, but at the cost of violating Intel’s design specs, and putting more stress on the CPU. However, overclocking in its essence violates Intel’s design specs, so you’re not breaking any new ground with this feature. I do not enable load-line calibration on my daily/gaming system. But I always use it when I am trying to fine the absolute limit. For more insight on the matter, refer to this excellent explanation at anandtech.com.
CPU Voltage
That brings us to the first thing that most users want to play with after powering up their new system for the first time: CPU voltage, aka “vcore”. As you can see, this is actually one of the last things you should be changing. I would recommend starting at a nice and easy 1.3V. Surprisingly enough, many users are able to achieve very good overclocks with this modest amount of CPU voltage.
Testing for your highest stable CPU frequency
Once the operating system has fully loaded, start up RealTemp. Now start up CPU-Z and verify that your overclocked settings have been properly applied, and that you are running at your desired CPU, bclock, and memory frequencies. Now start up you selected test program, for example OCCT or Prime95. Run the test for five minutes. Then reboot and go back into the BIOS.
If the test ran without error, the raise the bclock by 10MHz, reboot into your OS and run the test again. If the test failed, raise the CPU voltage by 0.025V, reboot into your OS and run the test again. Continue to raise bclock or CPU voltage until you meet one of the following criteria:
- You reach your desired bclock and successfully pass your test.
- You reach your maximum safe CPU voltage.
- Raising the CPU voltage does not allow for additional stability.
Maximum safe CPU voltage
For there is no maximum “safe” CPU voltage in my book. My recommendation is to determine your maximum safe voltage based on your temperatures while running your stability test. With stock air cooling this could be as low as 1.3V on some i7 CPUs while running OCCT. Or it could be as high as 2.2V when attempting Super PI 1M with an i5 670 on liquid nitrogen. Personally, I don’t like to see my load temperatures exceed 90C on air or water cooling, but it’s really up to you.
Is it stable?
So, once you find your highest CPU frequency by meeting one of the criteria above, lower the bclock by 5MHz, and run your selected stability test until you are satisfied. If you are looking for a stable system as a power user or gamer, OCCT or Prime95 for six hours is more than sufficient in my testing, but you may run longer if you desire. But for a true test of stability, I always like to play Crysis while encoding a Blu-Ray movie into an mpeg4 format.
Final Words
Well, that about wraps it up. Believe me, there is so much more to overclocking. There are SO MANY settings you can continue to fiddle with, but this guide should get you 95% of the way in 5% off the time. If you enjoy overclocking you system, I highly recommend joining one of the teams at OCForums. If you like to push your system and you like to get competitive, look into joining one of our great folding teams, or the OCForums Benchmarking Team. You’ll learn a lot and have a blast!
Please feel free to comment, and post any questions you have in the thread linked below where the great OCF community will help you out with any problems you may encounter!
3 Step Guide to Overclock Your Core i3, i5, or i7 is a post from: Overclockers – The Performance Computing Community
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