Intel LGA1156 Core i3/i5/i7 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 accept you to get extra performance for free. In this case, 3 components will be overclocked: CPU, RAM 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 LGA1156 (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.

Benchmark Reviews recently launched our Opinion & Editorials section. The reason I'm telling you this is because we published a little article called: "Desktop Platform: Killed by Overclocking". What it mentions is true. PC brands have taken control of overclocker's market and have evolved it to make it a feature/product which nowadays is a "must" for any PC component. I can't say overclocking has "died" with this kind of evolution, but many people consider it not as "pure" as it was before. Overclock has been made easy and there are big chances of watching people overclock their PC without knowing how does it works. Heck, many brands already include a basic overclock function/button in their motherboards which you just need to press and voila, you've overclocked your CPU/RAM in 2 minutes without any effort.

If you really love to overclock, you'll quickly start reading guides and comments about your components, as we always do it at first. Chances are that you'll be interested on getting extra performance with the best setup and you might start buying a new heatsink and super-featured (and expensive) components to reach your desires. Reality is, unless you're a "true" overclocker or love benchmarking every component, you'll stop at a point where you'll just want to get the best value for your money without buying expensive Extreme Edition CPUs or $700 USD motherboards with $300 RAM kits. This guide will show you how to overclock your Core i3/i5/i7 processor in a modest setup to obtain interesting gains without selling your kidneys to afford it.

I normally think we (people) need to take any advantage possible in our lives. If something is going wrong, just give it a 180º turn and learn what you need to learn from it. While brands have done overclocking as a "feature" of them, keep in mind they won't care about some people not wanting to take advantage of it, especially since they've got to compete between each other to produce the best products. So, let's take that advantage and overclock the hell out of our PCs while keeping them "safe" and to the point where you increase your efficiency instead of reducing it just for a few more MHz. Should we start now? Follow me to the next page...

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 this kind 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 they do hard-processing with their PCs, and some extra MHz will help with the video-codification, 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 overclock was done by BIOS or hardware modifications without having specific applications to test and control parameters are over. 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 P55/H55 platforms 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're 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 your RAM is working in Dual Channel mode (unless you've got 1 DIMM only) and your OS is recognizing all of it. NB frequency for LGA 1156 motherboards actually represents "Uncore frequency", so don't be fooled by CPU-Z, as P55 motherboards don't have a Northbridge. 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 incase it isn't, it will mean you'll need to decrease the memory divider/multiplier.

Additionally, if you prefer complex applications, you can use the latest version of CPU Tweaker. This tool works great in newest Intel platforms and it'll show you all the information showed by CPU-Z all in the same window. Also, you can expand it to show memory sub-timings which you can modify "on-the-fly" while testing in the OS. I use CPU Tweaker as my second tool because it shows everything I need, including Turbo or EIST technologies and Uncore frequency is not confused with NB frequency.

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. Perhaps, an interesting utility is ASUS Turbo V, which I'll be using today with my ASUS Maximus III Formula, mainly because every setting changed here is applied directly into the BIOS profile instead of OS/SW profiles like many other tools. This means you can actually test stability on your operating system and change values directly on the BIOS without restarting. Pretty cool, isn't it?

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 successfully run 30 hours of OCCT Linpack's test. I'm gathering all this 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 a 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 OCCT v3.1.0. Set it to run a pair of hours with medium data set and that will mean you'll have a PC stable enough to do heay tasks with the CPU. If you want to test maximum temperatures, CPU Linpack test is a must, since it loads the CPU higher than (almost) any other tool. Again, this tool isn't obligatory, but it's my favorite.

Since we're talking about 4 core CPUs here (Core i7 860), if I find OCCT failing after some minutes (or hours), 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. Both of these tools will let you test CPU stability and will also test RAM. 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 Prime95again and start Blend Test (uses lots of RAM). After a pair 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 which is the appropriate range of maximum temperatures. Have a look at the image above. If you add2 temperature" plus "Distance to TJMax" values, you'll find a TJunction value. For example: in this case 26+79 or 28+77=105. That's the maximum temperature you 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 Core i7 or the Core i5 750 processor, you might want to keep your temps below 80 degrees at full load (CPU Linpack OCCT test). Daily applications shouldn't stress it enough to pass 70-75 Celsius. For a typical Core i3/Core i5 Processor, temps should be lower, especially using a high-end heatsink like the one I used on my tests, which kept the CPU below 60 degrees at full load. Core i3 CPUs should be cold enough to be fairly overclocked with Intel's stock cooler, but try to keep your temperatures below 70 degrees. 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 were 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 pair of times without achieving it.

Now you should really have a look at your BIOS 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 i7 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. Low-end motherboards should reach around 170-180MHz BCLK, while high-end motherboards easily do 200+BCLK. Considering how high CPU multipliers are nowadays, a BCLK of 200MHz should be enough to reach decent speeds. Going above this might require increasing voltage on many motherboards.

QPI Frequency: QPI means Quick Path Interconnect. This is the newest Intel communication path which now communicates the CPU with the memory instead of passing through a North Bridge. QPI increases speed and bandwidth, so it is a very important value to be checked if you want the best clock's performance.

Uncore Frequency: CPU-Z reports Uncore Frequency as Northbridge frequency, which is false because there isn't a NB in P55/H55 motherboards. This value represents on-die memory controller's frequency and L3 cache's composing QPI frequency at the end. Similar to QPI and CPU frequencies, Uncore frequency is a Base Clock's multiple and it needs to be set at least twice the value of RAM frequency. Otherwise, your PC won't even BOOT. Increasing Uncore frequency gives a boost on overall performance similar to QPI frequency, but it can't be raised a lot. Example: If your memory runs at 1600MHz, your Uncore frequency should be equal to 3200MHz at least.

CPU Multiplier: As its name says, this multiplier gives you the final CPU frequency value. For Intel Core i7 processors, this multiplier is higher than LGA775 CPUs. This means BCLK doesn't need to be as high as FSB to reach outstanding frequencies. Normally, Intel determines a minimum of 20x for low-end CPUs while it can be set up to 25x-26x for high-end CPUs. Intel recently launched unlocked multiplier processors like the Core i5 655K used in this article. Those can reach up to 40x multipliers if needed without increasing BCLK.

RAM Memory Multiplier: This multiplier is directly affected by BCLK and results into a final memory speed. For example, if BCLK is running at 133MHz (stock speed), running a 2:10 memory multiplier should result into 666MHz for memory, which being Dual-Data-Rate based, results into 1333MHz. You'll have to keep an eye on this value or your memory kit will limit your CPU overclock while giving you head-aches trying to find which component is unstable.

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 easier the adventure 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.

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.

QPI/VTT/IMC Voltage: Increasing this value will be necessary when overclocking your BCLK and RAM frequency. It helps stabilizing RAM frequency, timings and QPI frequency too. If you're aiming for high BCLKs, you might need to increase QPI/VTT voltage. However, mid to high-end motherboards should be able to reach 200BCLK without increasing this value a lot (if needed).

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. VDIMM should be raised no more than 500 milli-Volts higher than QPI/VTT Voltage. Otherwise, you could permanently damage your CPU. Example: If your QPI/VTT voltage is set at 1.2 volts, VDIMM shouldn't be higher than 1.7 volts.

CPU PLL Voltage: You might need to increase this value when overclocking. Some people have found keeping this value at stock or even lower values helps achieving higher clocks. Don't over-volt this value a lot as it could quickly cause CPU degradation/damage. Leaving this in Auto-mode should be enough for 90% of our readers.

IOH Voltage: This value can help reach high BCLKs. Normally, letting it on Auto mode is enough.

ICH Voltage: It's best to set this on auto, as it powers the chip that keeps the communication from the CPU to peripherals.

How much voltage should I feed to my components?

Focusing on CPU vCore, the stock VID normally goes around 1.2 volts. If you're using stock cooling, you shouldn't go above 1.25 volts for 24/7 stability. In case you're using a high-end air-cooler or a water cooling system, then I'd recommend not going above 1.4 volts. In my tests, I used up to 1.5 volts to show you how little frequency vs. power consumption is gained from over-volting CPU with this range of values. Anyway, I don't recommend going above 1.4v unless you're using exotic/extreme cooling for benchmarking purposes.

About QPI/IMC/VTT voltage, it works around 1.1v-1.2v at stock conditions. This might be enough for low-medium overclocks, but higher values could be needed if you want to reach high BCLKs. Try keeping this below 1.5v in stock cooling. Also, remember this variable needs extra care to keep it in range with VDIMM Voltage as it was explained above.

VDIMM voltage is much more difficult to elaborate. Intel warns you not to pass above 1.65v, but people have proven going around 1.75v won't cause any damage to the CPU. Even that, I'd recommend not going above 1.65v, and if possible, try getting a low voltage memory kit (1.2-1.3v) as this removes stress from the Integrated Memory Controller. Unluckily, I can't tell you which voltage you should use for your memory kit since all of them are different and it all depends on which Integrated Circuit they are manufactured with.

Now that we've learned basic variables and how do they affect our overclock results, let's have a look at our testing methodology.

Overclock Testing Methodology

Let's start overclocking our LGA 1156 setup. First thing you might want to do is start overclocking your CPU. Since it's working at stock speeds with stock voltages, you might have a good gap to increase MHz before reaching its voltage limits. That might be the easiest step since your RAM or motherboard shouldn't be limiting to achieve it. But you should really start isolating CPU from all other components. For example, if your memory works at 1333MHz by default, try lowering memory multiplier to 1066MHz. Since you'll need to increase BCLK to increase CPU frequency, all other components related to BCLK will increase their value, and RAM memory could be limiting you.

In other cases, I'd also recommend lowering CPU multiplier and find you maximum BCLK if possible. Plan a target and try to find it depending on what you're expecting to reach. For example, let's say you want to reach 4GHz with a 20x multiplier. That means you need 200BCLK x 20 CPU multi = 4000MHz. Lower your RAM and CPU multipliers to the lowest possible setting and start increasing BCLK to reach 200MHz. If you're lucky enough, you will achieve 200MHz and then you'll know your motherboard won't be an issue. If you start raising your CPU along with the motherboard, you might hit a wall where you won't know if the problem relies on CPU or motherboard. Now imagine you also overclock your memory at the same time, and you'll end with a headache stopping you from trying and testing.

Once you've tested your motherboard, now it's time to increase your CPU frequency. Enter to your BIOS and set your CPU multiplier back to where it was initially and start increasing BCLK in 5MHz steps. Since many CPU multipliers will start at 20x or similar, each 5 BCLK MHz you'll be adding a total of 100MHz to CPU's frequency. Every time you add 5 MHz to the BCLK, you'll need to enter your OS and start doing stability tests as explained in the latest pages. If you think it is safe enough, you could try adding 10-15MHz to BCLK at the beginning, but eventually, you'll end adding 3-5MHz.

You'll end topping a wall where you won't be able to get a stable CPU. It's important to make BCLK increases in small steps, because your PC will be able to BOOT and it might enter to Windows, or at least you'll be able to change BIOS settings again to reduce values. If you do big BCLK increases, chances that you end with a PC not being able to POST are high, and you'll need to press the reset switch/jumper and start setting all things again. This can be very complicated if your motherboard is inside a small case, and unless you're able to save BIOS profiles, you'll need to remember and set all the parameters again.

Finally, after you've reached your maximum frequency, you might want to start adding vCore in 25mV steps (depending on your cooling) until you reach a stable frequency again. The process gets repeated until you've reached your maximum CPU frequency with the voltage desired. Keep an eye on temperatures while doing stability tests, as that should be a limiting for you depending on your setup.

Finally, it's time to overclock your memory and see what it can do. You'll need to save your CPU settings (or remember them) and lower the CPU multiplier again to isolate memory frequency from CPU frequency. Start doing the same process you've done with the CPU, but now with the memory until you reach a maximum frequency at a rated voltage and there you go. Now you'll need to find a balance between your maximum memory frequency and maximum CPU frequency. Let me tell you CPU frequency gives much more boost than memory frequency, so, CPU will always have higher priority in your balace's list. If, and only if you're reaching high BCLK MHz, you should start raising QPI/VTT/IMC voltage. But that won't be needed if you already tested your BCLK before starting with CPU and RAM frequencies. All other voltage values could be left on auto-mode and they might not be necessary to achieve what you want.

What if I'm "overclarking"my Core i3/i5? If you're overclocking your Core i3/i5 processor, you'll need to keep an eye on an extra variable: iGPU frequency. Unless you're using a dedicated GPU, you'll be using Intel GMA HD integrated graphics on CPU die. Of course, this parameter can also be overclocked (a lot, by the way), but you'll need to check it randomly to see if it's not limiting your CPU overclock. There are some motherboards where you can NOT detach iGPU from BCLK, and that's bad because your CPU frequency will be limited by your maximum iGPU frequency. Luckily, many motherboards have this option already unlinked or at least, they give you an option to unlink it so you can overclock your CPU without modifying iGPU frequency. Again, I repeat: If you're using a discrete graphics card (PCI-e slots), Intel GMA HD graphics unit should be disabled and the whole process will be easier (CPU could overclock higher).

Intel P55 Test Platform

• Processor: 3.2GHz Intel Core i5 655K Unlocked CPU
• Processor: 2.9GHz Intel Core i3 530 CPU
• Processor: 2.8GHz Intel Core i7 860 CPU
• CPU Heatsink: Noctua NH-D14 with NF-P14 fans
• Motherboard: ASUS Maximus III Formula P55 Motherboard
• System Memory: 2x2GB G.Skill ECO Series DDR3 (1333MHz @ 7-7-7-20)
• Video: Powercolor ATI Radeon HD 5850 1GB
• 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-Z
• Memtest 4.0
• OCCT Perestroika 3.0.1
• ASUS Turbo V
• Real Temp
• Prime95 - Blend Test
• CPU Tweaker

Overclocking Frequency vs. Voltage

In the chart, I decided to put Stock frequencies and label them as "No OC" voltage. Actually, the second category is stock voltage (still), but this time I'm overclocking those CPUs to find what they can reach without increasing vCore. This might be the more interesting achievement for those who are looking for a balanced overclock, and by balanced I mean little extra power consumption and almost the same temperatures compared to stock frequencies, while gaining many extra MHz. CPU's architecture allows them to increase their frequency by a lot of MHz before reaching their limit within stock voltage. That's done because Intel needs to make sure every processor will work within a good range of conditions no matter how bad they are, and that also lets them sell different versions (Core i5 650, Core i5 660, etc) with same voltage values and TDP. It's all about locking CPU multiplier to the speed they want to sell and it's done. That's why high-frequency CPUs like the Core i5 680 have less possibilities to overclock the same percentage compared to its little brothers.

Going back on to the chart, the Core i3 530 was able to reach 3950MHz before starting not being stable. That's 1 GHz OC (36%) with stock voltage, and the reason I say stock voltage overclocking is the most interesting and efficient setup. The Core i5 655K however, reached 4050MHz, which is great, but overall OC percentage would be 26%. Anyway, I can't tell how many people would love to have their CPUs at 4GHz with stock voltage. Some years ago, it was too sweet to be true. Finally, the Core i7 860 reached 3700MHz for an overall 32% OC. Considering this is a nice Quad Core CPU, I think the result is more than respectable. It actually overclocked more than the Core i5 655K (overall percentage).

Next step was to add 100 milli-Volts to the CPU vCore in order to see what we could reach with 1.30 volts. At this voltage, CPU is cold enough to be cooled by Intel's stock cooler and power consumption doesn't increases a lot yet. The Core i3 CPU sample achieved 4250MHz while the Core i5 655K achieved 4.3GHz. Both of these CPUs still remained below 55 degrees at full load, which is very nice. The Core i7 860 reached 3950MHz but the temperatures increased along with power consumption. I'll explain all those other measured variables in the next pages.

Finally, I set vCore to 1.4v and overclocked until I reached 4400MHz with the Core i3 530, 4500MHz with the Core i5 655K, and a very nice 4250MHz frequency for the Core i7 860. This would be the maximum voltage I'd ever suggest to use for a 24/7 overclock. However, I added some extra voltage to reach 1.5v and see if it was worth the time. I've included 1.5v results in the next pages just to demonstrate how bad would this setting be for a 24/7 overclock, even both Core i3 and Core i5 processors still managed to squeeze 200-300 extra MHz with this voltage. I didn't have to increase QPI/VTT Voltage for the tests as my motherboard scales very well at these ranges. However, it might be different in your setup depending on many variables like RAM, ambient temperatures, airflow and number of installed devices.

Overclock vs Power Consumption

As you can see, power consumption increases a little when you overclock with stock voltage. Maximum difference was 6 watts represented by the Core i7 860, while the Core i3 and Core i5 processors only increased 2-4 watts in idle mode. A 3% increment in idle mode compared to the 25-30% increase in MHz makes this look as the highest efficiency setup of all them. Anyway, we can only make conclusions after analyzing Full Load results, but I hope they won't increase that much. Increasing CPU vCore to 1.3v still adds a little percentage to the power consumption; however, the slope inclines a lot more when going to 1.5 volts as you can see in the chart. Now, let's have a look at Full Load (Prime95 Blend Test) results:

Ok, now we're talking... The Core i7 860 quickly reached 180 watts at full load, against 125-133 watts at load for the rest of the CPUs. Overclocking with stock voltage increased 3-4 watts on Clarkdale's processors while it increased 10 watts for the Lynnfield's CPU. In this case, the slope becomes bigger at 1.3v, especially the Core i7 860 which already passed 205 watts. The Core i3 is still doing fine with 10 extra watts over stock frequencies, and the Core i5 655K is consuming 15 extra watts compared to stock frequencies. I think it would be wise to say 1.3v is the maximum vCore accepted to keep efficient results at the end. Notice how the slope inclines a lot more with 1.4v and 1.5v? Those results make overall efficiency go down and you shouldn't apply it unless you don't care about power consumption or you're aiming for benchmark results only.

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

You've got to love that Core i3 530 CPU. This little chip has a TDP of 73 watts, and it consumes so little energy that it remains at 40 degrees at full load. That's something impressive. Overclocking it to 3.9GHz only increased this result by 1 degree. When I increased vCore to 1.3v, the temperature raised 5 degrees, and finally ended at 55 Celsius at full load with 1.5 volts. If you're using this CPU and you have a smaller heatsink you should be able to keep temperatures far below the limit (75C-80C) since we've got a 25 degrees gap before reaching it with this huge heatsink.

The Core i5 655K reached higher temps, usually 5-7 degrees higher than the Core i3, and that sounds fair considering it overclocks a little bit more. The interesting part is the small 2 degrees increment at stock voltage when overclocked to 4050MHz. I think running a CPU at 4GHz while having 47 degrees at full load is like being in heaven, and you'll be getting back what you paid for it. Finally, the Core i7 860 being a 4 cores processor is much hotter. It almost reached 60 degrees at full load with stock voltages (something we didn't reach with 1.5v on the rest of the CPUs), and kept rising until reaching 75 degrees with 1.5v, which basically is touching the limits of acceptable temperatures. Since you'll probably run it at 1.3v only (to reach 4200MHz) chances are that you'll keep your temps below 70 degrees. If you think that's still too much, then you'll have to live with stock voltage overclock, especially if your heatsink isn't good enough to handle those quantities of heat.

Intel Core i3/i5/i7 Final Thoughts

I hope I've covered the basics of overclocking in LGA 1156 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 to the moment you don't want to use your PC at stock settings again. This way, you don't only understand your PC in a better way, but it works as practice, in order to help you identify bugs and errors in different setups. You'll get costumed to identify 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 start in this scope, but are scared enough 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 will this impact in your heat production and power consumption. Also, you might be able to achieve similar clocks with similar setups. Just remember every CPU/RAM/Motherboard is different from each other, and that means you could get better results, as well as you could have worst results. But overall, I think this little guide will help you know what are the "common" values and limits of each kind of CPU.

I've chose the Core i3 530 as it's the smallest of its brothers, but the Core i3 540/550 CPUs should be able to run similar frequencies. The only kind of CPU I didn't test this time, was the Core i5 Lynnfield's CPU, also known as Core i5 750/760. If you have this processor, you should expect similar results to the Core i7 860 as it consumes the same (or more) watts and it's a Quad Core based CPU. If you're finding something missing in this article you'd like to see, comment it in our forums or comments section. Also, if you're starting to overclock your CPU and you are stuck in some part, post your results and we'll be glad to help you improve your settings.

Intel LGA 1156 Overclocking Guide Conclusion

As for conclusion, I can say there's no doubt on why LGA 1156 platforms got very famous compared to LGA1366 setups. Basically, you get a less expensive option while getting the same performance on the majority of the tasks. The Core i7 860 for example, matches very well the performance of the famous Core i7 920. Also, you're not "forced" to use triple channel memory kits and the platform still allows SLI/CFX depending on manufacturers. Overall, this is a very nice setup and it offers a lot of paths to update, starting with the Core i3 CPU which is the slowest but still very fast and capable CPU with integrated GPU, and up to the Core i7 875K which is one of the fastest processors at the time I'm writing this article.

Overclocking capabilities of Clarkdale's processors are quite good. Each CPU increases around 700MHz-1000MHz with stock voltage values, and they run quite cool even at full load. If you're looking for a 4GHz+ CPU with reasonable voltages and temperatures, keep those models in mind. You'll also get Intel HD graphics integrated in the same package in case you're thinking on HTPCs. The best part of these CPUs is the power consumption, which puts them as very good contenders for HTPCs while having enough power for heavy applications.

In the other hand, we have the Core i7 Lynnfield CPUs. They overclock well as I've shown in this article, but I think they're not on pair with the legendary Core i7 920 processor. The pros of this CPU against the Core i7 920 are that it will consume less power and probably run colder also. This Lynnfield CPUs have very strong memory controllers, so, if you're aiming for 2000+MHz memory kits, you'll need one of these to pair it with your RAM frequency. Remember, if you want to know the benefits of overclocking your CPU in real numbers/benchmarks; don't forget to read our Featured Reviews: Processors section.

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