Skylake Non-K Overclocking Performance Tests
Few days ago the overclocker DHENZJHEN uncovered the Skylake Non-K overclocking capabilities of the Supermicro H170 mainboard and set serveral new top scores on HWBOT.org with an overclocked Intel Core i3 6320 at about 5 GHz. He also found out that the overclocking limit was only caused by the BIOS itself. There was no special hardmod needed to overclock the Core i3 6320 which usually has a stock clock of 3900 MHz.
Unlike K-CPUs which can be overclocked using the multiplier, Skylake Non-K overclocking can only be done using the BCLK. Pre-Skylake CPUs such as Haswell or Devils Canyon could only be overclocked by about 3-5% using the BCLK because the BCLK was still tied to the DMI and the PCIe.
Skylake Non-K Overclocking Basics
However, for Skylake CPUs, BCLK and PCIe have a dedicated reference clock which always stays at 100 MHz – no matter how you change the BCLK. In other words: You can push the BCLK without worrying about other components.
This gives great overclocking opportunities in theory. Some overclockers at HWBOT came across a BCLK wall of 102.8 MHz after they tried the new i3-6320 in the Intel XTU Benchmark. It was quite obvious that it was a natural wall so people started to try to bypass this limit.
So far ASUS and ASRock showed some pretty impressive results on liquid nitrogen cooled setups. ASUS published scores today with a LN2-cooled i3-6300 clocked to 5800 MHz for multithreaded benchmarks (elmor i3-6300 @5800 MHz Cinebench).
Apart from the impressive extreme overclocking results, this is amazing in many ways. Intel stopped the “free overclocking” with Sandy Bridge by introducing the K-CPUs. Skylake Non-K overclocking is a Throwback-Thursday for the whole overclocking community and also great for 24/7 Overclockers to save a lot of money.
Luckily I have quite good access to hardware (thanks Caseking!) and just grabbed some CPUs from the warehouse to do some testing.
|CPU Name||Core Count||Stock Clock||Turbo Clock||Hyperthreading||L3-Cache||Price|
|Pentium G4400T||2||2900 MHz||-||No||3 MB||70 €|
|Core i3-6320||2||3900 MHz||-||Yes||4 MB||160 €|
|Core i5-6400||4||2700 MHz||3300 MHz||No||6 MB||185 €|
|Core i5-6600K||4||3500 MHz||3900 MHz||No||6 MB||260 €|
|Core i7-6700K||4||4000 MHz||4200 MHz||Yes||8 MB||400 €|
- ASRock Z170 OC Formula (Find at Amazon)
- 2 x 4 GB TeamGroup DDR4 3866 MHz
- NZXT Kraken X61 AiO (Find at Amazon)
- Windows 10
I used the ASRock Z170 OC Formula to test the CPUs. All you need is a special BIOS which you can download here:
- Enter the BIOS and go to the OC Tweaker – DRAM Configuration.
- Load the XMP Profile to adjust your memory correctly
- Adjust the BCLK to the level you need (see picture above with i5-6400)
- Adjust the DRAM Frequency to the correct level. I had to stay below 2800 MHz on the memory to achieve high BCLK clocks
- Go to: OC Tweaker – Voltage configuration
- Set 1.350 fixed core voltage. Leave everything else on auto.
My i5-6400 turned out to be great and I could even run 4725 MHz on 1.375 Volt which equals an incredible overclocking of 75 %.
The only problem about the “special BIOS” is the fact that you can’t read out the core temperature. No matter which tool you use, you will always see 100°C. However, after clocking a lot of 6700K CPUs I can tell that anything below 1,40 Volt is fine with proper cooling like the X61 Kraken. Even cheap and weaker air coolers can handle these CPUs at up to 1,40 Volt. Especially the i3 and Pentiums CPUs only produce a small amount of heat.
I didn’t have much time so only tested Prime95 quickly but as you can see 170 BCLK was no problem for a quick test. According to the Kraken Software there was close to no heat so you can be sure that these values are safe (clock and temperature-wise).
Skylake Non-K Overclocking: Cinebench R15
I did some quick Cinebench testing because you can compare multi-core and single-core performance pretty well with other CPUs. For Skylake CPUs I kept the memory between 2600 and 2800 MHz depending on the memory divider and BCLK.
The single-core performance is pretty important for applications and games which don’t scale well with multithreading. The 70 € Pentium G4400T is doing pretty well overclocked to about 40 % and even matches the i7-4790K. Both, i3-6320 and i5-6400 beat the high-end 6700K when it comes to single-core-performance.
Multithreading is the real deal and you can see that the Pentium G4400T has no chance against the other CPUs – even overclocked. However, the Pentium comes close to the i3-4370 which costs twice as much as the Pentium. The i5-6400 performs amazing considering the price of only 185 €. Overclocked by 75 % you can come close to the i7-4790 which costs over 300 €. All in all – amazing!
Skylake Non-K Overclocking Conclusion
It’s surprisingly easy to overclock these CPUs on the ASRock board. ASRock did an amazing job with the new BIOS. There is nothing you have to take care about apart from Base-Clock, Core-Voltage and Memory-Clock. I could reach the 75 % OC within 10 minutes without any special settings or CPU-binning.
It’s also pretty obvious that the CPU clock is not limited by the BCLK. 170 MHz was no problem using the i5-6400 whereas I could not even reach 120 MHz using the i3-6320. So I advice to get cheap CPUs with low CPU multi and push the BCLK.
Of course it makes no sense to get an ASRock Z170 OC Formula in combination with a Pentium G4400T. However, it’s just a matter of time until we will see unlocked BIOS for cheap Z170 or even H170 boards. In the end this is still the best OC-News since Sandy-Bridge considering the fact that I could gain +75% OC which results in +52% performance.
If you have any questions, don’t hesitate to ask in the forums: