Intel Sandy Bridge Overclocking Guide

Editor's Note: Before starting, you should know that any kind of overclocking normally invalidates your product's warranty. While many products come pre-overclocked, brands usually don't expect you to get extra performance for free. In this case, 2 components will be overclocked: CPU and motherboard. If you're a beginner, read the whole guide before starting, or (better) print it to have it around while your PC is being tested. Benchmark Reviews won't be responsible for any damaged component caused by overclocking.

I know, the first paragraph makes it look like a very dangerous action, but don't be scared, it isn't. In fact, I can tell you that every CPU tested in this article is completely alive and running 100% stable at the moment of publishing this article, even I tested with "dangerous" voltage levels. If you're a beginner or you haven't overclocked any LGA1155 (or similar) platform before, you need to understand the basic concepts of the commonly-used variables and the process of overclocking: raise frequency, test stability, confirm and raise frequency again until you can't complete this sequence anymore.

Before starting I need to say we would have written this guide a couple of months ago when Sandy Bridge was launched along with the H67 and P67 platforms. However, Sandy Bridge platforms suffered a 2-3 months delay thanks to a small error in the P67 chipset design. Users with B2 revision motherboards might find troubles with S-ATA 2 ports in long term use. While this was supposed to happen after 2-3 years and only to about 5% of the products shipped, Intel quickly took action on this and aborted all shipments asking manufacturers not to provide their motherboards to the distributors and resellers. Intel acted quickly enough to stop Sandy Bridge distribution besides some re-sellers, reviewers, media sites and a small portion of people who ran of to the store and bought their Sandy Bridge platform. Within the end of March and beginning of April, many brands announced they would start shipping Sandy Bridge Motherboards again, and here we are now.

The Rules have changed

Intel launched a pair of "special" processors for the LGA 1156 platform; the Core i5 655K and the Core i7 875K. Those processors were supposed to bring better overclocks without any limits. However, many of us already expected this to be part of a new methodology, in which Intel would end shipping those processors and limit all non-K processors to their stock frequencies. This happened with Sandy Bridge. The thing is that you can't overclock any non-K processor way beyond its default frequency anymore. Non-unlocked processors are stuck to Base Clock (BCLK) overclocking, which happens to be so poor with this new platform that it won't give you more than 100-200 extra MHz before reaching the limit.

Intel also got platforms separated as the P67 platforms represents a mid-high segment and the H67 platform represents a segment where the user wants to take advantage of the integrated graphics unit in their CPU. H67 platforms can't overclock with non-unlocked processors, but even worst, they won't let you OC your unlocked processor either. So again you're stuck to BCLK (if any) overclocking, but in exchange, they'll let you overclock your iGPU to some decent levels.

While there are speculations about the Z68 platform, we're still stuck at the middle of the arena mainly between the H67 and P67 platforms. Let me put it straight: if you want to overclock, you need a K processor with the P67 platform. Any other combination will result in very poor overclocking capabilities. Finally, let me add that while X58 and P55 platforms overclocked to a 200+ BCLK easily, Sandy Bridge won't give you more than 3-7 extra MHz. YES. That means the limit on Sandy Bridge motherboards lies between 103-107MHz, which is just nuts.

Why Should I Overclock?

Actually, the question is: why should YOU overclock? There are many reasons to enter the great world of overclocking. At first, it was a necessity. People had slow PCs doing heavy processes where any extra MHz would reduce time in a linear way. If a 100MHz processor was clocked to 120 MHz (20MHz sounds ridiculous, doesn't it?), an enterprise could do the process in 8.5 hours instead of 10, thus increasing efficiency. Nowadays, it's very different. Computers have become part of our daily-basis life, and 90% of the people don't use it for heavy processing anymore. Many things can be done with a PC, as it has been turned into the new primary communications tool; CPUs are much faster and normally more than enough for daily tasks. For these kinds of people running several light-loaded applications while reading Benchmark Reviews and hearing some music, a basic overclock should be more than enough. Others might complain that they do hard-processing with their PCs, and some extra MHz will help with the video-encoding, 3d rendering, math processing or any other hard task. For those who fall in this category, a medium-sized overclock should be a great addition to work with, and we're covering that today.

Overclocking Applications & Utilities

Times when overclocking was done via BIOS or hardware modifications without having specific applications to test and control parameters have come to an end. In fact, we have plenty of different applications where we can monitor all our components and utilities to test how stable our machine is after the changes. In our Overclocking Guide for Beginners , we already published a list of utilities and tools for overclocking. Two years later, things haven't changed a lot. In fact, we still use the same tools posted in that guide, which is good news for "new" overclockers or people who might want to re-try it after some years being out of action. I've chose some tools supporting the latest P67 platform because that's what we're testing today. Don't worry if you feel too overwhelmed with information, the whole list will be written in the CPU Testing Methodology section.

Our first tool is a "must" between the utilities used today. CPU-Z, developed by CPUID, is a very simple, yet complete application to check our components. There are some labels I'd like to explain here as they will be key to monitor your advances. So, open CPUz.exe and the next window will appear in your monitor:

CPU tab will show you basic information of the installed CPU, and if you want to overclock it, here is where you'll be 90% of the time. Please notice you can check CPU model and Core voltage in real time. Below, you can check the Core Speed, CPU multiplier, Bus Speed (BCLK or DMI for LGA1156 motherboards) and QPI frequency. Those will be the most useful values after all, and they all contain necessary information to achieve the best overclock.

Let's jump to the third tab. This will show you the Motherboard's manufacturer and model. More important, it will show the chipset and the BIOS version. Check your BIOS version and your manufacturer's page in order to confirm you have the latest version available as it might include enhancements and features along with a wider support for CPUs/RAM.

The next tab is called "Memory", and it will be important as you can monitor RAM frequencies and timings. Check that your RAM is working in Dual Channel mode (unless you've got 1 DIMM only) and your OS is recognizing all of it. P67 motherboards don't have a Northbridge, thus, NB frequency is grayed out. Finally, check your timings to match with those in the specifications (for beginners) and don't forget DRAM frequency actually represents Dual Data Rate MHz, so, if you're reading 800MHz it's actually 1600MHz. DRAM frequency will increase along with BCLK, so you'll need to monitor this frequency to keep it stable or in case it isn't, it will mean you'll need to decrease the memory divider/multiplier. Sandy Bridge unlocked CPUs allow you to overclock your CPU without increasing a single MHz in your RAM frequency, leaving it out of the equation. This is good and bad at the same time, because it means you won't have head-aches while overclocking your PC because you don't know your RAM, and because it won't limit our final OC. However, this also means your RAM won't be overclocked and the memory Bandwidth won't increase as it did in other platforms. If you're an avid overclocker you'll overclock your RAM after getting to know your CPU to get some extra MHz as usual.

Since I'm using an ASUS motherboard I'll use ASUS AI Suite II as my support application. AI Suite is one of the best applications I've ever seen for enthusiasts. In this case, Turbo V EVO along with all the sensors will be very useful to check frequencies, temperatures, voltages and other configurations. Turbo V EVO also changes frequency and voltage values in real time without restarting or applying profiles that need to be loaded at windows start, so that's a nice plus. If you have another motherboard from a different brand, I recommend checking their official page in order to get their overclocking software.

Many brands have developed their own overclocking tools and many of them work great while having friendly user interfaces. If you want to achieve the best compatibility with your motherboard, you should check the official manufacturer's page and look for their tools. Brands like Gigabyte, ASUSTeK, MSI, ASRock and Biostar have been working hard to offer you monitoring tools were you can overclock and check temperatures in a graphic/visual interface. Some other brands like Gigabyte and ASUSTeK have gone wild, enabling some pretty interesting features like "hardware overclocking", on-board buttons, LCD posters and wireless monitoring utilities.

Processor Stability Testing

Before starting, I must say stability is a concept that can be perceived in different ways depending on your needs. While some people think SuperPi runs are enough to check stability, others want their PC to successfully run 30 hours of OCCT's Linpack test. I'm gathering all these concepts into a PC stable enough to do daily applications no matter how hard they are because that's what we're aiming for. I would be unsatisfied if my PC suffered a BSOD while doing multi-tasking, playing my favorite game online or coding and rendering the next-day's project. What you must understand, is that every component needs to be tested in different situations to check if it's 99.9% stable. In this case, since we're overclocking our CPUs (mainly), my favorite tool is Prime95. Run it through a Blend Test to check both CPU and Memory stability, or run in place large FTT for maximum heat and power consumption. Usually, a couple of hours means your PC isn't prone to suffer BSODs, but I prefer to leave it running at least 10 hours before working. Usually, a night running Prime95 should be enough.

Since we're talking about 4 core CPUs here, I usually fire up Prime95 and start doing Blend tests. Prime95 allows you to check which CPU core is failing, and so you can add voltage or compensate the CPU knowing which core is the weakest of all. However, if you're just starting to overclock your CPU, you might want to test it with something lighter, and Cinebench R11.5 is a good choice to ensure CPU is (at least) stable enough to boot into OS and open your OC tools. Even Cinebench uses all your available cores; it won't define any kind of stability by itself.

Next step would be testing your RAM. RAM is a little bit more difficult to test because while you can spend 10 hours running stability tests, it could fail while opening a very simple application (e.g.: Photoshop, MSN messenger, etc.). What I do is: start with MemTest and put all unused RAM to test until it reaches 100% (at least). Many people think this is enough, but RAM can be a real pain if you don't stress it enough. Try opening Prime95 again and start Blend Test (uses lots of RAM). After a couple of hours running Prime95, you might want to check with your daily applications and GPU benchmarks like Unigine's Heaven 2.1. Trust me; RAM fails exactly when you don't expect it to fail, so it's better to make sure it will be stable enough for hard daily work.

You might be wondering what the appropriate range of maximum temperatures is. Have a look at the image above. If you add "temperature" plus "Distance to TJMax" values, you'll find a TJunction value. For example: in this case 28+70=98. That's the maximum temperature your CPU will support before turning the computer off for self-protection. Of course, it's very unlikely to reach these temps, and motherboards normally have protection limits somewhere between 80-90 degrees. That's why it's actually very difficult to burn a CPU nowadays unless you're giving it too much voltage.

If you're overclocking a Sandy Bridge processor, you might want to keep your temps below 70-80 degrees at full load (Prime95 FTT test). Daily applications shouldn't stress it enough to pass 70-75 Celsius. Keep in mind CPU temperatures are meant to be kept below those limits at overclocking conditions. Thanks to the 32nm manufacture, you might be able to keep your CPU below 60 or even 50 degrees at factory settings (no OC, no extra voltage). Now that you've downloaded and understood your weapons, let's get a little bit more technical and analyze all the variables you should pay attention to while overclocking. In the next page I'll explain each variable and how to control it from your BIOS/OC utility.

Understanding OC Variables

There are some basic variables you should really check while overclocking. Based on these variables, you'll be able to achieve 90% of your overclocking process and actually reach a stable and very decent frequency without messing a lot with weird numbers and values. Please refer to your motherboard's manufacturer to locate the BIOS reset switch/jumper before starting to overclock. This jumper will be very helpful if you reach a completely unstable state where the PC won't BOOT anymore. Don't panic, just turn off your computer and press/short the appropriate pins to reset your settings. Some other manufacturers implement an auto-recovery feature which (in case the PC doesn't BOOT) will recover your settings after trying to POST a couple of times without achieving it.

Now you should really have a look at your BIOS/UEFI and identify the section where all the next parameters are found. If there's a possibility to save different profiles (many motherboards feature multiple OC profiles) save a copy of your default's profile.

CPU Frequency: This frequency is calculated by multiplying CPU multiplier x BCLK. Until Intel LGA775 sockets, this frequency was calculated by multiplying CPU multiplier x Front Side Bus. Intel Core iX processors changed this FSB for a Base Clock (BCLK) which is the basis to all the parameters I'll explain below. CPU frequency is 100% related to overall speed, and thus, it's the most important factor when overclocking your setup.

BCLK: This value is the key to obtain all other values, since all of them are BCLK multiples. I won't really go deep into this value as its overclocking capabilities are way below they used to be. 100MHz is the default value but you can usually get 3-5 extra MHz or even a little bit more if you happen to have a good CPU+Motherboard.

CPU Multiplier: As its name says, this multiplier gives you the final CPU frequency value. For Sandy Bridge processors, this multiplier is higher than LGA775 CPUs. This means BCLK doesn't need to be as high as FSB to reach outstanding frequencies. With Sandy Bridge unlocked processors, this is the key to get a superb overclock. While the theoretical limit is 57x, many processors stop at 53-54x. I wouldn't be mad at that as that means I could get more than 5GHz, which is a frequency normally impossible to stabilize.

RAM Memory Multiplier: This multiplier is directly affected by BCLK and results into a final memory speed. Since we're not overclocking the BCLK that much with Sandy Bridge platforms, memory won't affect that much.

CPU EIST & Speedstep: Properly used, this technology allows CPU frequency transition between low and high states. By changing CPU voltage and lowering CPU frequency, the CPU is able to consume less power at idle mode, while increasing values whenever any process is detected. Those features can be very useful if you want to overclock your PC while keeping low temperatures and power consumption at idle mode. Unluckily, many manufacturers disable these features when you start overclocking, letting CPU voltage/frequency at their max state all the time.

Turbo Boost: This feature is inherent to Core i5/Core i7 processors only. By monitoring which cores are processing information, Turbo Boost allows them to increase CPU multipliers individually for each core, increasing final speed by 1 to 4 multiples while the rest of the cores (unused) remain at stock speeds. It's best to disable this feature when overclocking since that will make it easier to find your CPU's sweet spot. However, you can set a lower CPU frequency and let Turbo Boost reach your maximum tested overclock if you prefer.

Load-line Calibration: Also named as vDroop compensation or LLC, this feature increases CPU voltage to balance it between different states. At full load, CPU vCore droops to keep levels at Intel's specifications. While enabling LLC will give you the ability to run more MHz with "lower" voltage, this feature falls against Intel specifications, and it's not recommended, especially when you're aiming to increase vCore a lot. With Sandy Bridge introduction, LLC has become a very important value to enable in order to achieve high overclocks. Many people found that LLC enabled their CPU to reach way higher CPU multipliers, so, most of the motherboards in the market now support LLC.

PCI-E Frequency: Normally set at 100MHz, this value could help a little while overclocking your system and GPU. Try keeping it below 115MHz as it could produce S-ATA drives corruption. I normally set this value to 101MHz as a rule.

Voltage Values

CPU vCore: This value is related to CPU frequency. If you want to get extra MHz, you'll need to add vCore to your CPU. CPU vCore is also 100% related to CPU temperature and final power consumption. With Sandy Bridge, I'd recommend keeping it below 1.4-1.45 volts. Normally, a 4 core CPU running at those voltages will reach 70-80 degrees even with a high-performance cooler.

VCCSA: This is the System Agent voltage which in this case means Integrated Memory Controller. Since Sandy Bridge IMC has proven to be very robust, it's not really needed unless you want to reach super high memory frequencies or while using all the 4 memory slots. Usually 1.15v should be OK for anything and many overclockers recommend not going above 1.2 volts.

VDIMM/DRAM Voltage: Related to RAM memory, you'll need to increase VDIMM voltage to achieve higher RAM frequencies. Contrary to CPU vCore, different RAM kits need different voltages and they might get to a point where adding voltage won't help anymore depending on the integrated circuits (ICs) built on your memory kit.

UEFI: BIOS gets a new look

Intel P67 Test Platform

• Processor: 3.3GHz Intel Core i5 2500K Unlocked CPU
• Processor: 3.4GHz Intel Core i7 2600K Unlocked CPU
• CPU Heatsink: Noctua NH-D14 with NF-P14 fans
• Motherboard: ASUS P8P67 WS Revolution P67 Motherboard
• System Memory: 2x4GB G.Skill Ripjaw X Series DDR3 (1333MHz @ 9-9-9-20)
• Video: ASUS ENGTX 560 Ti
• Disk Drive 1: Intel X-25M 80GB SSD
• Disk Drive 2: Seagate Barracuda 1TB SATA
• PSU: Antec Signature 850W
• Operating System: Windows 7 Ultimate x64

Applications & Utilities

• CPUID CPU-ZROG Edition
  
• ASUS Turbo V EVO
• Real Temp3.67
• Prime95 - Blend/FTT Test
• Unigine Heaven 2.1 Benchmark

Overclocking Frequency vs. Voltage

As you can see, both Sandy Bridge processors have a vCore around 1.1 volts. This is the reason Sandy Bridge achieves pretty good temps at load conditions at factory settings. The first step was bumping CPU frequency to 4GHz. For this, I just increased CPU multiplier to 40x and added a few milli-volts to the vCore. Both processors were able to achieve 4GHz with 1.15v, which is a very outstanding result. Let's keep in mind that Lynnfield and Nehalem processors needed more voltage (around 1.3v or more) to achieve 4GHz. The only processors able to reach 4GHz almost at stock voltage were the Core i3 and Core i5 Clarkdale CPUs, but all of them worked with 2 cores/4 threads.

With Sandy Bridge we're not going to break any record at 4GHz, so my next step was passing to 4.4GHz. I'd say this is the best frequency according to CPU temperature and power consumption. It required something around 1.25v to keep both processors rock stable. Up to this point, it seems both the Core i5 and the Core i7 require similar voltages to achieve the same frequencies. However, let's not forget that the i7 has 2MB of extra L3 cache and works with Hyper Threading technology.

Finally, I set my highest stable point at 4.8GH. I needed almost 1.4v for the Core i7 and 1.4v for the Core i5 in order to achieve a stable platform here. With those voltages, the CPUs reached the limit and the temperatures raised a lot against stock settings. Just for fun, I tried getting 5GHz stable without any success. I would need a better motherboard and probably a better heatsink with more than 1.45v in order to achieve my dream, but I didn't want to risk any of my CPUs just for a test.

Overclock vs. Power Consumption

OK now we're talking. The Core i7 2600K consumes 10 extra watts against the Core i5 2500K at full load. When overclocked to 4GHz, the i5 increased 16 watts while the i7 increased 17 watts. The next step was overclocking both CPUs at 4.4GHz which according to the voltage it needs; it seems like the sweet point for Sandy Bridge overclocking. The Core i5 increased its power consumption to 82 watts, which is 23 extra watts against stock values, while the i7 increased to 94 watts, nearly arriving to the TDP.

Finally at 4.8GHz the Core i5 consumes 90 watts, which is 50% extra consumption, while the Core i7 2600K reaches 105 watts, representing a 50% extra power consumption also. Of course, increasing power consumption means the CPU heatsink will have more watts to dissipate, thus increasing CPU temperatures. Let's have a look at our voltage vs. temperature results in the next page then.

Overclock vs. Temperatures

At idle mode my Core i7 seems to be colder than the Core i5 processor. Only when increasing voltage and CPU frequency, the Core i7 rises up its temperature to the point where it matches the Core i5 temperature. This is however a non-important case as they're both at idle mode. The real deal will appear in the next chart after I make them pass 30 minutes of Prime95 FTT test:

At stock frequencies both CPUs are quite cold. They don't even reach 50 degrees, which is great for any PC. At this point the Core i7 is colder than the Core i5, which seems natural after watching the CPU power consumption charts. At 4GHz the temperature raised to 51 degrees for both processors. At 4.4GHz the Core i7 2600K raised its temperature to 59 degrees while the Core i5 2500K reached 57 degrees probably because it's got less thread and cache. Finally, at 4.8GHz the Core i5 reached 67 degrees and the i7 reached 74 degrees. Remember that limit between 70-80 degrees? That means we shouldn't put any extra voltage to the Core i7, while the Core i5 still has got a little gap to test. Anyway, it's always better to keep your CPU below 70 degrees.

Intel Sandy Bridge Final Thoughts

I hope I've covered the basics of overclocking the Sandy Bridge platforms in this article, and even more, I hope to persuade you to try it with your PC, as you don't really have anything to lose, while you have a lot to gain. When someone starts overclocking, it becomes a passion at that moment, and you don't want to use your PC at stock settings again. This way, you not only understand your PC in a better way, but it works in practice, in order to help you identify bugs and errors in different setups. You'll get accustomed to identifying variables and fix both hardware and software errors and the best part is that you'll feel satisfied with yourself as you start knowing better, each part of your PC.

More than analyzing the enhanced performance of an overclocked system versus a stock one, I hope to have prepared the terrain for those who want to start overclocking, but are scared to try it with their PCs. The reason I did all the tests with each processor was I wanted to show you an example of what you can achieve by overclocking, and how this will impact your heat production and power consumption. Also, you might be able to achieve similar clocks with similar setups. Just remember every CPU/Motherboard is different, and that means you could get better results, as well as you could have disappointing results. But overall, I think this little analysis will help you to get to know with the most "common" values and limits of Sandy Bridge CPUs.

We are close to 0 extra versions to test as we don't have any other unlocked CPU at the moment. At the time I'm writing this article, there are some signs of the Z68 chipset, which will be some kind of a hybrid between P67 and H67, but until then, we're stuck with a P67 platform and the Core i5 2500K and the i7 2600K processors.

Intel Sandy Bridge Overclocking Guide Conclusion

I want to end this article by letting you know that I'm very impressed with the overclocking abilities of the new Sandy Bridge processors. Intel made the whole overclocking process easier, and the clocks we reach with the new processors are just insane! The bad thing is that we're now fully limited to certain chipset and processors to do so, while the rest of the CPUs are fully locked to their Turbo frequencies. In the past, getting a Core i3 and overclocking it like hell was very fun, as it represented a very competitive product in the low-mid market. With Sandy Bridge there won't be any more overclocked entry-level setups, or overclocked HTPCs.

Also, there's always the point of learning and having great skills to understand how different settings and variables work, but with Sandy Bridge all things are easier, and that means more people will be able to compete or achieve high clocks without reading and visiting multiple different sites and forums as they did before. It's just a win-lose paradigm, depending on which side of the road we are positioned. I must also add that sub-zero overclocking was pretty fun to do. Intel somehow killed this as it seems Sandy Bridge CPUs won't clock that high at subzero temperatures, and the difference is minimum.

We are all expecting to see new unlocked CPUs (perhaps a Core i3 unlocked edition) and the Z68 platform along with Ivy Bridge and the new 2011 socket to see where's the future going, but meanwhile, we can get some fun with air/water coolers and the actual Sandy Bridge CPUs now that the S-ATA bug is no longer on B3 revision motherboards.

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