I7 - 2600K / I5 - 2500K Overclocking Guide


To begin, I would like to say that overclocking(OC) is not something to take lightly. While it can be greatly helpful to OC your machine to better performance, any attempt to OC a machine can result in a multitude of things: voidance of warranty, decreased life of you hardware, and possible destruction of your hardware, etc. With that being said, please read and understand all the intricacies of your hardware to ensure you have full knowledge of what it is capable of and set a goal you want to reach on STABLE clocks only. I, BestOfMedia, and TomsHardware are in no shape or form responsible to loss of hardware, decreased life, or voidance of warranty. Please OC at YOUR OWN RISK and take the time to fully understand before starting/considering any type of OC. This is what the forums are for: to help you understand overclocking. Ask plenty of questions before you undertake such an endeavor.


The objective of this thread is to show you how to OC a machine to STABLE clocks for increased performance. My personal goal was to see how high of a stable clock I could reach without machine failure.

For my setup, the following equipment was used:

Motherboard: MSI P67A-GD65 Intel Motherboard.
Processor (CPU): Intel Core i7-2600K Sandy Bridge 3.4GHz, 4 x 256KB L2 Cache, 8MB L3 Cache, LGA 1155 Quad-Core Desktop
RAM: G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 PC3 12800
Power Supply (PSU): CORSAIR CMPSU-850TX 850W ATX12V 2.2
WaterCooling Heatsink/fan (H2O): CoolIT SYSTEMS ECO-R120 Advanced Liquid Cooling
Graphics Card (GPU): GRFX Card: XFX HD-695A-CNFC Radeon HD 6950 2GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Video Card


With those listed, let’s get started. To OC, there are many factors that you will need to consider and understand to successfully OC your machine. Like stated before, the goal is to achieve a higher yet, stable clock to increase performance. You do not necessarily have to reach the highest clocks possible on your machine or obtain the highest clocks available on the internet; we just want to focus on improving the performance of an already stable chip/chipsets. With the newer motherboards (mobo) and BIOSes with the P67, there are some new things that you can or cannot do. With the MSI GD65, it comes with the new ClickBios for those who do not want to fumble through scrolling and gives a GUI (Graphical User Interface) for those less knowledgeable in that specific area. While I do not prefer the ClickBios (as I found myself still using the up/down/right/left keys), this can be beneficial for those who enjoy mouse interaction within the GUI. Another thing I noticed was the lack of the ability to fine tune the FSB (Front Side Bus) and/or the BCLK. It seems that the CPUs/BIOS lock the multiplier (or CPU Clock Ratio) and this is now your main utility for OC purposes. Therefore, you will increase or decrease the multiplier instead of BCLK/FSB (a standard +/- 5-10MHz is possible but anything more or less than that causes system failure.)

First, you want to make sure your heat sinks are seated correctly and you probably want to put some arctic silver, diamond paste, or some sort of thermal paste on the heat sink before fully seating. To do this, just get some thermal grease or paste and apply it to the heat sink sparingly. A small dot of this on your heat sink or CPU is all that is needed, as too much can actually decrease performance. The purpose of these products is to fill in the small, minute imperfections in the dies to maintain a solid connection between the CPU and your heat sink.

Next, you are going to want to update the BIOS of your motherboard to the latest version.

Next, thing you want to do is start your machine up at stocks speeds and completely wipe and reinstall windows. This allows a fresh install so there are not any extra drivers or cached info that could lead to lack of stability. After the fresh load, make sure you update all of your drivers for the mobo, GPU, hard drives (HD), etc so you have the latest versions.

Afterwards, you are also going to want to load all the windows patches, again so you will have the latest setup completed.

Before any clocks are increased or decreased, it would be prudent to download some monitoring tools to see what is actually happening in windows.

A few of these are(links to the software are provided at the end of this article):

HWMonitor – provides volts and temps of your hardware
CPU-z – provides real time processor frequency, vCore volts, Ram speeds, and temps.
Core Temp/Real Temp/Speed fan – provides temperatures of your hardware.
SuperPi/HyperPi/Prime95 – provides the ability to produce a full load on your system to monitor temps and clock speeds in the previously stated programs.

Glossary of terms:

In this section, I will be going over some of the terms that will be used so you can understand completely what each setting means and why or why not to “mess” with it and show the risk of “messing” with it.

VCore or VCC: This is the actual amount of voltage supplied to your CPU from the PSU and is control by the mobo/BIOS. This is integral to all OC but especially with the newer Sandy Bridge processors as increasing this provides stability for higher clocks.

LLC (Load Line Calibration)/Vdroop Control: This is a setting that tries to eliminate Vdroop and Vdrop when your CPU is under load. Vdroop is implemented so that when your processor is under extreme or full loads, voltages and amperage are increased to your CPU to maintain stability and makes sure your CPU stays within the allotted thermal design power. Basically, VxA=W or Volts times Amps = Watts. Meaning, that if you increase volts/amps it gives you higher wattage and in turn gives you more heat and heat is counterproductive to all OC and PC setups. Vdroop/Vdrop is setup to decrease the instability by increasing the wattage to the CPU. However, this causes more heat inside the case and, as stated before, can cause lower clocks to be achieved.

Vdroop: Again this is your CPU increasing/decreasing your volts/amps/watts to stay within the thermal design under load conditions.

Vdrop: This is your mobo decreasing voltage across the board no matter what is manually set by the BIOS.

VDDQ: This is your Ram volts. It is basically from the Stub Series Terminated Logic; the electrical standard for all driving transmission lines to DDR and SDRAM implementations

VCCPLL or phased locked loop: This is the voltage of the internal clock on your CPU. (Controlled by the mobo/BIOS and is most likely shown as PLL)

VCCSA: This is your System Agent Voltage. It powers everything that is not controlled by the PLL. It controls the allocated power to your CPU.

Here we go:

We are now going to get down to OC the machine. Well, here we go. After setting up a fresh install, loading all the newest drivers, and updating the BIOS, restart your machine and go into the BIOS. This is normally done by pressing the delete key while the machine is in the POST phase. Once done, you should see a simple GUI for bios settings. While most BIOSes have a failover that automatically reset to default in the event of a failed OC; we still want to make use of the saved ability within your BIOS. After each stage of successful clocks, load test, and temp test; Save that setting to one of the allotted slots within your BIOS so you can always revert back to a stable clock and do not have to reconfigure the settings for that clock each time. It is not necessary to save the default clock, as it is normally reverts back or you can revert back via a jumper, dipswitch, or button on the mobo. For this OC, we will not OC the RAM from the start so please keep those at the default settings for now.

First, let’s enable or disable some settings for proper OC.


Limit CPUID Maximum
Power Technology
C1E Support
OverSpeed Protection
Spread Spectrum


Internal PLL Overvoltage
Execute Disable Bit
Intel Virtualization Tech

Note: For the MSI motherboard these settings can be found in the following sections:

In your main Overclocking Menu you will see:
Internal PLL Overvoltage
Spread Spectrum

If you scroll all the way down to the bottom of the section you will see "CPU Features." In here you will see the options for:
Limit CPUID Maximum
Power Technology
C1E Support
OverSpeed Protection
Execute Disable Bit
Intel Virtualization Tech

Doing these are pretty much needed to maintain a stable clock and to OC in general. After these are set, go into your main CPU area of the BIOS. Right now, besides all the things you just changed, everything should be set to default.

On the 2600K, your default clock is 3.4 GHz or 3400MHz and should be displayed as that. Below this you will notice a setting for the Computer Base Frequency (otherwise known as FSB or BCLK), it is displayed in KHz so do not let the 10000 frequency confuse you. This is what I was saying can no longer be clocked too much as these CPU’s are mainly locked to the multiplier or CPU clock ratio. Below that setting is the actual Clock Ratio and what we will be using for this thread for means of OC. It should say “34”. To explain this is what is multiplied by the core frequency to get your base clock. So 34 x 10000Khz = 3400MHz or 3.4 GHz. Increasing this will effectively multiply your base clock by 10000KHz. So adding one will take your multipler to 10000KHz by 35 giving you 3.5 GHz. Before setting any voltages, we will use this to increase the clock of the machine until instability; this will allow you to find out how high your machine can go before messing with voltages and increasing heat, decreasing stability, and possible voidance of warranty.

So increase the multiplier by 1 and load into windows and check your temps and run superpi or another preferred program to test the load to the machine. This is vital to do after each step up for informational purposes. Eventually you will get to a clock that will either fail to boot, cause a blue screen in windows, crash after load is applied, or completely freeze. (In my case, it was mainly blue screens.) After we find out the stable stock clock, we can tweak a bit.

[Note: In MOST cases, you will be able to clock to 4.3 – 4.7 GHz before the system begins to fail.]

After you reach a stable stock OC Clock, save your BIOS settings into one of the allotted slots. This, again, allows for you to revert to these settings as a standard.

So you want higher clocks:

While a clock of ~4.5Ghz is excellent starting point (effectively a ~38% increase on your clock), most of you are asking “How can I get higher/more stable clocks?” Well, this is where you begin upping the voltages to each applicable setting to provide more power to your CPU, RAM, etc. This will increase stability but at the cost of heat and too much voltage can cause complete hardware failure, so I cannot stress enough; PLEASE BE CAREFUL AND UNDERSTAND FULLY BEFORE ADJUSTING VOLTAGES!!!

Voltage and their extremities:

Refer to the following to understand your limits before setting. While most can be increased with no problems, you can fry stuff and void your warranty at higher voltages.

VCore: Stock is 1.3v and should not be raised higher than 1.5v
VCCSA (System Agent): Stock is 0.925v and should not be raised higher than 0.971v
VDDQ (RAM VOLTS): Stock is 1.5v and should not be raised above 1.65v (this depends on the manufacturer of the RAM, so please note when you buy it.)
VCCPLL (Phased-Locked Loop): the stock is 1.8v and should not be raised over 1.89v
VCCIO (I/O Supplied voltage): The stock is 1.05v and should not be raised over 1.0815v

In most setups, there should never be any reason to increase either the PLL or the SA. PLL can be raised but should remain stock as you can apply too much power to your CPU and cause hardware failure. SA should also not be touched as it is a fixed voltage and controls what your VCore ultimately is. However, with that being said, if you wish you can change these to either decrease Vdroop or raise the voltage to your Vcore and results will be increased clocking.

Now with the voltage standards out of the way, here comes the integral part in clocking your machine higher. You will want to adjust each one of these separately to ensure a stable clock and so you can find out which one is causing instability. So with an increase of the multiplier, start with your Vcore and raise one setting higher(smallest amount possible) until you get a more stable clock. Afterwards, boot your OS and run some stress testing to ensure stability. Wash, rinse, and repeat. After Vcore, choose the next voltage and change it, but do NOT go above the limits stated above as it can cause the problems listed above. Do this for each step of the multiplier increase until you reach a stable clock (no blue screens, no crashes, no random reboots, etc.)

After you get a stable clock (either the highest possible out of your chip or the goal you set in the beginning), then you can change the RAM settings, voltages, timings to increase performance. With that being said you can lower the clocks on your RAM (1333MHz or 1600MHz depending on the make/model) to the lowest clocks (800Mhz is the lowest) to boost your CPU OC higher at the risk of losing timings, read/write speeds, etc.) The goal of this whole process should be to find the clock you want at stable under load, use the least amount of energy (lowest stable voltage changes), and have a completely, stable OC machine.

For my setup I was able to reach a stable clock of 5.1GHz and maintain a 45-47C on all four cores under full load. And all of this was at the lowest possible voltage settings to increase the longevity of my hardware. Hopefully, this explains how to OC your Sandy Bridge and get the maximum possible value out of its potential. Be safe and have fun with your newly OC’d machine.

If there are any questions, concerns, comments, improvements; Please feel free to send me a pm.

My CPU-z Report

Links for Clarity:

Monitoring Tools:
- HWMonitor
- CPU-z
- Core Temp
- Real Temp
- Speed fan
- SuperPi
- HyperPi
- Prime95

Explanation of terms used:
VCore or VCC:
VCCPLL or phased locked loop:

Technical Data Sheet from Intel referring to the i7, i5, and i3 processors

- Data Sheet

Warning: This guide is officially the property of Toms Hardware and Best of Media, no unauthorized copying, or reproduction is allowed.
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