Intel SkyLake Overclocking Guide



You overclock your system at your own risk. Overclocking your CPU could cause the CPU to fail, or reduce its useful life. Neither nor myself will take any responsibility for any damage that may be caused to your CPU or system by following this guide.

Overclocking guide for Intel 6th generation Core processors (SkyLake).

If you are an extreme overclocker then this guide is probably not for you. What I intend to cover in this guide is a sensible CPU overclock that can be used 24/7, and all without power consumption going through the roof.

There are many ways to overclock these CPUs and I’m not going to claim that this way is the best way, but simply that it should work for 95% of the people who would like to get some extra grunt from their CPU without the need for extreme cooling solutions, or having to worry about power consumption getting out of hand.

First of all, let’s cover what you will need to successfully overclock a SkyLake CPU.

The first thing of course is a CPU with an unlocked multiplier. For SkyLake that would be a CPU model with a “K” at the end, 6700K for example. Overclocking these CPUs is simply a matter of stepping up the multiplier. Of course it isn’t quite that simple, as you will need to watch how much voltage you push through these CPUs, and also that stepping up the voltage and clock speed will inevitably produce more heat.
SkyLake can also be overclocked using a base clock method, where you leave the CPU ratio alone and clock the system using BCLK. Or you can use a combination of CPU ratio and BCLK to achieve your desired overclock. For this guide, I will only use the simpler core ratio method of overclocking the CPU.

The next thing you will need is a chipset that allows the CPU to be overclocked. For this we will need a motherboard with the Z170 chipset. At the time of writing this guide, the Z170 chipset was the only one available.

A high end cooling solution.
If we are going to look at overclocking seriously then the first thing you will require is a high end cooling solution. The SkyLake 6600K and 6700K CPU’s do not come supplied with a stock cooler. This should tell you that the cheap Intel stock coolers supplied with previous CPU generations are not up to the task, even at default CPU speeds on this platform.

Some important things you will need to keep in mind.
SkyLake and the Z170 chipset are very different from the previous generation of Intel Core processors and chipsets, and it has taken me a few weeks to learn and understand how to overclock this platform properly. In order to get a safe and reliable overclock on this platform is going to require voltages to be changed that if set incorrectly will damage the CPU, RAM, or motherboard. So please read the voltage settings and warnings very carefully.

With a new platform come some unexpected issues with what you may consider a stable overclock. An example would be that I had overclocks that were stable during a 30 minute run of the AIDA stability test, but the system would refuse to recognise a USB stick when inserted into a USB port. After this, the system wouldn’t close down. After much trial and error, I finally tracked this issue down to DRAM stability, and as we’ll discover a little later, DRAM stability on this platform is not quite as simple as it sounds, even at default DRAM speeds of 2133MHz.

Let’s get started.

For this guide I will be using the following hardware and software.
• CPU: Intel Core i7 6700K CPU (SkyLake)
• Motherboard: Asus Z170 Deluxe, with UEFI version 0801
• Corsair Vengeance LPX 2666MHz DDR4
• CPU cooling: Be-Quiet Dark Rock Pro 2 (high end air cooling)
• Power Supply: Antec 550 Watt modular (Important. The PSU must be compatible with Haswell or later CPU’s, and support those CPU’s low power states)
• OS: Windows 10 Pro 64bit
• CPU voltage monitoring: CPUZ.
• CPU temperature monitoring: RealTemp• Stability testing (quick): CineBench R15
• Stability testing (full test): HandBrake X264 video encoding.

The maximum core temperature is as follows.
• TJMax is 105c

If TJmax is reached then the CPU will throttle back to prevent permanent damage to the CPU die, but you don’t want to get to close to those temperatures. For SkyLake, 85C really shouldn’t be exceeded for any prolonged period.

Measuring vcore voltage.
This is the amount of voltage that is being supplied to the CPU cores.
You will no doubt have seen on some overclocking sites, that people are pushing crazy amounts of voltage through the CPU cores, in order to get that last 100MHz of speed. For this guide we will be a bit more conservative and sensible.

The maximum safe voltages for 24/7 use are as follows.
• High end air cooling 1.35 volts
• High end water cooling 1.40 volts
Measuring the core voltages is again very easy, and free. CPUZ is probably the best option for this.

Overclocking the CPU.
To actually overclock the CPU, we are going to do this through the UEFI (BIOS), and as I said at the top of the page, we are going to do this without sending power consumption through the roof.

First of all you will need to enter the UEFI (advanced settings), and you will need to consult your motherboard manual as to how you enter the UEFI (advanced settings).

Asus Z170 Deluxe main UEFI screen

From the main screen we need to select the advanced mode option, and then select the Ai Tweaker option.
Once you have reached the Ai Tweaker screen, the first things you need to set are the following.

• Ai Overclock tuner = Manual
• BCLK frequency = 100Mhz
• Asus MultiCore enhancement = disabled
• CPU core ratio = Sync all cores.
• Core ratio limit = 43. (we will start at 43, as most SkyLake 6700K should be able to reach this speed without issues.

For the moment, we will just set the max core ratio, and won’t bother with DRAM or iGPU overclocks, as it’s important to check stability before overclocking the RAM or iGPU.

The next thing we need to set are the voltages.
First we will set the CPU core voltage. For this, we will use the ‘Adaptive method’. This method is much safer, and consumes less power than a fixed core voltage.

Take great care when setting the following voltages.

First select ‘Adaptive mode’, and an offset mode sign as +
Now let’s set the offset adaptive voltage. You can see in my example, that my 6700K requires an ‘adaptive offset’ of 1.320 Volts. Your’s may require less voltage or more, but do NOT exceed, 1.35V with high end air cooling, and no more than 1.4V for high end water cooling.

Next set your DRAM voltage, and make sure you do NOT exceed the manufacturers recommended setting, and for sure do NOT exceed 1.35V DRAM voltage.

If you are using a single DDR4 DRAM module, then you can leave the CPU VCCIO voltage and the CPU System Agent voltage on AUTO. If you are using a dual channel DDR4 kit, then you will most likely need to set a manual voltage for VCCIO and system agent.

Be very careful here, as setting this voltage to high will almost certainly damage, or kill your CPU.

CPU System Agent voltage should NOT exceed 1.25V
CPU VCCIO voltage should NOT exceed 1.2V

Spend some time tuning the system agent and VCCIO voltages, and get them as low as possible whilst still maintaining stability.

Having implemented all the above changes, save the settings in the UEFI, and see if the system will POST and boot Windows to the desktop. If it does reach the desktop, then start monitoring the CPU core voltages and temperatures. If all seems ok, then open a few applications, and make sure you have stability. I also recommend that you plug in a USB device, and make sure it’s detected and working. If all seems ok, then we can proceed to a quick stability test.

Download and run CineBench R15, and run the CPU benchmark on all cores. Keep an eye on core voltages and temperatures whilst it runs. If it completes without issues, and the CPU temperatures are fine, then you may wish to go for a higher CPU clock speed by increasing the core ratio one step at a time, each time checking core voltages and temperatures each time you clock the CPU faster.

If you have a good 6700K then 4.6 GHz should be achievable on high end air cooling, and perhaps 4.8GHz on high end water cooling. My own 6700K can reach 4.8GHz with ease, but my air cooler can’t keep it cool enough for 24/7 use.
Once you reach your MAX stable overclock, where core voltages and temperatures are fine, then I suggest you take it down one step, and then run the FULL stability test.

Unless you’re into distributive computing, where the system will be at full load for perhaps days on end, then the traditional ‘stress tests’ such as PRIME95 and AIDA stability test are completely unrealistic for this platform.

I’ve found using HandBrake with an X264 video encode, where it lasts between one and two hours is a much better test for real world stability on this platform. Whilst doing this test, I strongly recommend that you keep an eye on temperatures.

Overclocking the DRAM
Overclocking the DRAM is much more difficult, but well worth the effort, as tests have shown that higher DRAM frequencies on SkyLake has a large impact on performance.

The default DDR4 frequency on SkyLake is 2133MHz, any DRAM said to support faster speeds is overclocked. If you have purchased DDR4 memory which claims a frequency higher than 2133MHz, then you will require the memory specifications, voltage, frequency, and timings from the memory manufacturer. You will need a bit of luck in getting the DRAM to run at the claimed speed with your CPU overclock. Be patient, and do not exceed the recommended voltages for the DDR4.

Setting the DDR4 frequency
Providing you have set the DRAM, CPU VCCIO, and system agent voltages from the CPU overclock section, then you can proceed as follows. First select the ‘DRAM Frequency’ from the drop down menu, and then go to the DRAM Timings page, and enter in the required timings from the manufacturers specifications.

Save the settings in the UEFI, then make sure the system will POST, and boot Windows to the desktop. Then repeat the stability tests from the CPU overclocking section of this guide. Once again, keeping an eye on voltages, and the temperatures.

Please keep in mind that the CPU’s and the motherboards quality will have a say on how fast your DRAM can run, so don’t automatically blame the DRAM if it can’t reach the manufacturers claimed speeds. It could be the memory controller inside the CPU just can’t cope with that speed, or the design of the traces on the DRAM circuit of the motherboard just isn’t good enough to support that speed.

iGPU overclocking
You can also overclock the iGPU (internal graphics processor) on SkyLake. The default frequency of the 530 iGPU found in the 6700K is 1055MHz, with a BCLK 100/20 ratio. As you can see from the screenshot below, I have mine clock at 1300Mhz with a BCLK 100/26 ratio. The maximum mine seems to support is a BCLK 100/30 ratio, but I have not experimented with voltages, where perhaps I could reach faster speeds.

Well, that just about covers this guide, have fun experimenting, but do use safe voltages and keep an eye on temperatures.

I’d be very interested in your SkyLake overclocking exploits, so feel free to share your findings below.



When a new platform is launched, things don’t always go to plan, and when the launch date of SkyLake and the Z170 chipset was brought forward by a month. The scope for something going wrong increased.

This was the case with Z170 chipset motherboards. The Intel Management Engine Interface (MEI) had an issue with f-clock (FCLK). FCLK is a clock generator which is responsible for data interconnections between the CPU and the rest of the system, and most importantly from a performance perspective, the PCIe3 interface.

FCLK is set by Base Clock (BCLK), typically 100MHz plus a multiplier. for SkyLake DT (Desktop SKU), FCLK should have been set 100MHz x 10 to give a resulting FCLK of 1GHz.

However, a bug in the MEI firmware meant that when FCLK was set at 1GHz, the system would fail to POST. In a rush to get their Z170 motherboards out in time for launch, motherboard manufacturers down-clocked FCLK to 800MHz, while they waited on a firmware fix for MEI from Intel.

The firmware fix is now available, and should be made available from the motherboard manufacturers via a BIOS (UEFI) update. In order to be able to set FCLK to 1GHz then MEI firmware version ending 1168 or later is required. You can normally check which version you have by entering your motherboards UEFI (see the screenshot below).

Assuming your motherboard has the updated MEI firmware update, then look through the advanced settings for FCLK in the UEFI.
Asus has added this option on the Ai Tweaker page, under the ‘Tweakers Paradise’ menu.

Set the value to 1GHz, or BCLK x 10.

Once set then graphics performance with a discrete graphics card should receive a boost, as should high performance PCIe3 SSDs connected to either of the two main PCIe3 x16 sockets which are connected directly to the SkyLake CPU.


Thanks for the article, very helpful!

dunno why with same cpu and essentialy same motherboard (z170 premium) and following your settings, I can only get max 4.7 and min voltage of 1.36


I’m just got a dell xps 8900 with an i7 6700. I’m going to gut it and get a good z170 mobo, psu, memory, and bclk this baby up. Tossing in an EVGA GTX 980TI FTW… :slight_smile:
Has anybody here blck’ed an i7 6700 non-k?


Open to recommendations for a good z170 mobo.


I have used the Z17-A by ASUS along side with a 6600K and I was pleased by its performance when it comes to overclocking and also very well build, but if my friend could afford it I would have opted for the deluxe board.

That is the only experience that I have with Z170, hope it helps.


Yo Harley, read this before you try to Oc that 6700


Saw that Alan. I have seen newer posts where it says that there are bios updates available for a plethora of z170 mobos which allow non k overclocking.


Intel released a microcode update that prevents BCLK overclocking a non K part, and will almost certainly have found its way into all new boards by now.
There are some hacked BIOS around, but its a risky business using one of those with a new board and CPU.

Also, you will require quite a beefy cooling solution it keep it all running cool.


Since this was a Dell refurbished that hopefully was sitting on a warehouse for awhile, it is worth trying. No matter what, I was planning to swap my $500.00 xps i7 6700 to a better case, change psu, and faster memory which would require a better mobo anyway
So only thing I will be out to try the bclk oc, is a better cooler. I will go with a decent watercooler. I’m thinking Corsair C70 case, gskill 3000 ddr4 2x8 cl15 (reviews show it will oc well), already have evga gtx 980 ti ftw, 850w psu, and I’m still reading reviews trying to decide which mobo to go with.questions


Hi, sorry to ask such a stupid question but I am currently configuring my first self-build PC and want to make sure that I don’t mess up somewhere. Regarding the change of the FCLK from 800MHz to 1000MHz: I have an AsRock Fatal1ty Gaming K4 motherboard and an Intel i5 6600k processor. Even with later Versions of MEI than 1168, AsRock’s default for the FCLK is still 800MHz with the option to set it to 1GHz. Is it considered OCing, when I do this and thus makes me lose my warranty? Because in theory, both components are made to work with 1GHz FCLK.
Thanks in advance,