Overclocking A Skylake i5 6600K

Interested in building a new Skylake gaming PC and thinking about overclocking it? This article will break down what you need and what you can safely expect to get out of an unlocked Intel 6600K i5 CPU with the right motherboard & cooler.

Disclaimer

Proceed at your own risk, overclocking can result in system instability or even hardware damage that may not be covered by warranty. Evatech takes no responsibility for any such issues and advises anyone who maybe uncertain about what they are doing to stop now.

The Requirements

  • K series Skylake CPU, either the 6600K or 6700K.
    We went with the 6600K as the better value for money option, with benchmarks online suggesting once overclocked it can achieve the same if not better results as the 6700K (also overclocked) particularly in gaming.
  • Mid to High End Z170 Motherboard
    B & H series boards do not support overclocking and the cheaper Z series boards may not get you the best results. We went with a MSI gaming series Z170 board, the Z170A Krait.
  • 120mm or 240mm Enclosed Liquid CPU Cooler
    A little cheap cooler is the last thing you want if your going to be attempting any serious over-clocking at all but a gaint custom DIY liquid cooling setup is overkill. We split the difference and went with a 240mm solution from Corsair but the Cooler Master or DeepCool

Other components don’t effect the overclocking process all that much if at all so feel free to pick what suits your needs best. That being said don’t try to save money on the power supply, a good high quality power supply will be much more stable and likewise cheaper power supplies can introduce stability issues especially in overclocked environments. We went with a 650W 80+ silver power supply, 16GB of 2400MHz RAM, a GTX 980TI and a 500GB SSD to round out the build.

The Method

All the settings and options can be a bit much to take in at first glance but if we keep it simple, there are really only 5 settings we need to pay attention to.

  • The base clock speed
  • The base clock multiplier
  • The ring clock multiplier
  • The CPU voltage.
  • The CPU SA voltage.

These can all be adjusted in the motherboard BIOS and are typically tucked away in the advanced settings options. The final CPU speed is the result of the base clock speed multiplied by the multiplier (eg the stock settings of the 6600K is a base clock of 100MHz and a multiplier of 35 resulting in 3.5GHz).

The simplest method is to incrementally increase the multipliers, with each step up, saving and rebooting the PC, and checking its stability. If you overstep your boards, the motherboard will simply not boot and you will need to reset your BIOS and start again, so make sure you make a note of your last stable boot settings!

At a point, you won’t be able to increase the multiplier without also increasing the voltage. While messing with the multiplier is relatively safe, the voltage settings have a little more potential to wreak havoc and need to be treated with a little respect. “Overvolting” can damage or lower the life span of the CPU and is the single biggest contributor to increasing the operating temperatures. To play it safe, we would not recommend exceeding 1.3v.

Below is a list of each setting we attempted as we incrementally pushed the clock speeds and voltages higher.

[Multiplier x Base Clock @ CPUv / SAv Core Voltage]

  • 38x 100Mhz @ 1.175v / 1.175v. Result : Boot Successful.
  • 40x 100MHz @ 1.175v / 1.175v. Result : Boot Successful.
  • 42x 100MHz @ 1.175v / 1.175v. Result : Cannot Boot.
  • 42x 100MHz @ 1.200v / 1.175v. Result : Boot Successful.
  • 44x 100MHz @ 1.225v / 1.175v. Result : Cannot Boot.
  • 44x 100MHz @ 1.275v / 1.175v. Result : Boot Successful.
  • 45x 100MHz @ 1.285v / 1.175v. Result : Boot Successful – Windows BSOD.
  • 45x 100MHz @ 1.290v / 1.200v. Result : Boot Successful.
  • 47x 100MHz @ 1.290v / 1.200v. Result : Cannot Boot.
  • 47x 100MHz @ 1.300v / 1.200v. Result : Boot Successful.
  • 48x 100MHz @ 1.300v / 1.200v. Result : Boot Successful.
  • 49x 100MHz @ 1.300v / 1.200v. Result : Cannot Boot.

Remember that some CPUs will better suited to overclocking that others, even if they the exact same model, it’s just the luck of the draw and it comes down to minute imperfections on the manufacturing process. You may be able go further that we did, or not get so lucky, but from similar results we can find online, our final overclock was well within the average.

Why didn’t we mess with the base clock? Well we did, and every single time we attempted to charge it the system refused to boot or failed our burn in tests so for the purposes of brevity we stripped the base clock altered results out of the list.

Stability & Thermal Testing

Just because the system booted with your settings in place, doesn’t mean your overclock is stable. The next step is to stress test the CPU and make sure it doesn’t crash or exceed its operating temperatures resulting in system lockups or automatic under clocking. To test for stability we performed hour long Prime95 tests, a free piece of software available widely online that places all cores of the CPU under their maximum load possible. With Prime95 running we used CoreTemp, also free, to monitor system temperatures.

Our highest bootable setting of 4.8GHz at 1.3v passed our hour long test but exceeded 75C under load and climbed as high as 35C at idle. While this is still within safe operating temperatures we dialed it back to 1.290v at 4.5GHz and re-ran our tests. At 4.5GHz the idle was only 29C and the max only reached 62C. We also noticed that the CPU cooler fans stayed quieter, not needing to spin up to their maximum speed during our stress test.

The Final Result

4.5GHz @ 1.285v (1000MHz over the stock base clock) idling at 29C and maxing out at 62C under full load with plenty of room to push towards the 5GHz mark if if your feeling lucky and don’t mind the loud hum of hard working CPU cooler fans.