Overclocking: What and Why?
Overclocking began years ago as a way to get that little extra out of your computer hardware, "a free upgrade", as many have put it. Since the olden days, overclocking has changed. Overclocking has become not only a way to gain extra performance, but also a way for users to customize their hardware and make it their own. The truth is the inner feeling of accomplishment that comes with running your hardware faster than anything sold on the market is almost as important as the utility gained from the boosts in speeds. Many in the industry love to use the analogy of cars to explain usage models for enthusiast hardware, and in this case, that analogy holds true.
Those who upgrade, tweak, and modify their computer hardware do so for many of the same reasons people upgrade, tweak, and modify their cars. The feeling of accomplishment and the feeling of really making something your own is why people work so hard to make small changes, and in my opinion, the added performance boosts are a bonus. Overclocking your CPU not only improves raw horsepower in tasks such as video rendering, but it also helps alleviate possible bottlenecks in your system where the CPU might not be the focus. As games become more wonderful, GPUs become more masterful, and flash storage becomes more plentiful your system might require a CPU that is more powerful. This guide will not only show you how to overclock your CPU to its maximum potential for 24/7 use but also outline how to alleviate any system bottlenecks and stabilize the system. To start things off, I will cover the basics of overclocking Intel Skylake.
Attending IDF this past August provided some insight into Intel's stance and progress on overclocking. Intel's introduction of the "K" SKU and the Performance Tuning Protection Plan (PTPP) shows that Intel is supporting overclocking, but it's not free. While it is true that only Intel's K SKUs are meant for overclocking, something else comes with the extra letter. Intel has begun to focus on overclocking and has taken overclocking into consideration in the design stage of the CPU. I would bet that overclocking was a requirement for the new CPU, and we all know that requirements are only requirements when there is some potential for ROI. Theoretically speaking, if you bought a K-SKU CPU from Intel, that extra money didn't only go to the shareholders, but also back into producing CPUs with better overclocking features.
What's special about Intel Skylake?
A high-level overview is provided by Intel on how the CPU is setup, there are a few multipliers missing (mainly cache and FCLK), but overall this is how Skylake is setup for overclocking. I will dig into this on the next page.
After discussions with some of the engineers who designed Skylake, it was apparent that they made some changes to improve overclocking. The most major was the decoupling of the PCI-E/DMI bus from the rest of the frequency domains (CPU core, cache, and memory), and allowing motherboard manufacturers to use an external clock generator for the BCLK. Other improvements are increased memory multiplier granularity (from 200/266MHz on Haswell to 100/133MHz increments), support for DDR4 4133MHz, and general overclocking improvements regarding unlocking voltages for end users.
Haswell and Broadwell both employed an integrated silicon-based voltage regulator (FIVR), which allowed for single rail input from the motherboard and better control over internal voltage domains. While the FIVR isn't being used in Skylake, it does seem that an integrated linear regulator is present in Skylake (according to David Kanter of The Linley Group) but is disabled in the cores but not in the uncore (uncore means "not the core").
Regardless of the impact of this linear regulator, there are now many voltage rails the motherboard must provide the CPU instead of just one. Compared to pre-FIVR CPUs such as Ivy Bridge/Sandy Bridge, Skylake has a comparable number of input rails, five of which are pertinent to this guide.
How this guide will work
I have written overclocking guides for every single Intel CPU since Sandy Bridge, and usually made it easier on myself by using one motherboard and one CPU. For this guide, I decided to make things infinitely harder on myself by using five different high-end overclocking motherboards from five different companies (out of 20+ Z170 motherboards I have), four CPUs, and two very-high-speed memory kits. I spent almost two months testing and gathering data, a few weeks analyzing the data and making pretty charts, and I spent the better part of last week going through endless BIOS shots, screenshots, and datasheets to get all the information you might need.
I like to analyze overclocking semi-scientifically, and to do this, I spend a decent amount of time thinking up tests and how to run them to maintain consistency and reproducibility. To make things simpler, I have picked a few benchmarks, taken the scores, and then averaged and normalized. CPU Benchmark performance uses scores from CINEBENCH, HandBrake, and AIDA64 while memory performance uses AIDA64. The scores are then equally weighted (for CPU scores synthetics and real-world scores are weighted equally) and charts then utilize percentages starting from 100% to more easily show changes. I hope you enjoy and benefit in some way from this guide, and if you have any questions, please feel free to ask in the comments section below!
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- Page 1 [Introduction to Skylake Overclocking]
- Page 2 [Disclaimer and Before You Begin Overclocking]
- Page 3 [Overclocking Flow Chart, Non-K SKUs, BCLK, and Multipliers]
- Page 4 [BCLK, Core, Cache, Memory, and FCLK Scaling]
- Page 5 [Skylake Overclocking Voltages]
- Page 6 [Power Savings and Voltage/Power Analysis]
- Page 7 [The Durability of Intel's 14nm Node]
- Page 8 [Skylake Memory Overclocking: Corsair and Frequency Scaling]
- Page 9 [Skylake Memory Overclocking: G.Skill and Memory Timings]
- Page 10 [ASRock Z170 Overclocking: Z170 OC Formula]
- Page 11 [ASUS Z170 Overclocking: Maximus VIII Extreme]
- Page 12 [EVGA Z170 Overclocking: Z170 Classified 4-Way]
- Page 13 [GIGABYTE Z170 Overclocking: Z170X-SOC Force]
- Page 14 [MSI Z170 Overclocking: Z170A XPOWER GAMING TITANIUM EDITION]
- Page 15 [Stability Testing, Delidding, Crashing, and Throttling]