Introduction

One of the most exciting things for PC enthusiasts is the launch of new hardware, but that excitement comes from a different point for those that like to overclock. The launch of a new platform is an opportunity for overclockers to explore tweaking from a different, new angle by traveling down the path of an "early adopter" and achieving never-before-seen performance. Being the first to discover new tricks, mastering the platform's greater options, is a temptation many enthusiasts fail to fight, and I myself have fallen victim to it time and again. Playing with settings is something I cannot get enough of, and Intel's latest Haswell CPUs pose an interesting mix, tempting me with new options and challenges. Word across respected review sites is that Haswell's overclocking performance might be a bit underwhelming, with most reviewers being rather unimpressed by what it offers, and in general, I have to agree.

Be that as it may, I do think Haswell has been underestimated, and part of that is due to the huge complexity of Intel's latest. So to see if I couldn't find something to help us "normal" users get a little more, or at least as much as was offered by Ivy Bridge and Sandy Bridge, I got myself a few chips and set to finding the limits of what is offered. I read every overclocking guide companies would give me, watched all the marketing information, spoke to high-profile overclockers spending their time on attempts at breaking world records, and even started a thread here on our forums to poll normal user results in an effort to get the most amount of information in the shortest possible time. I managed to kill a few chips too, which I hadn't done in some time, but Intel has thrown down the gauntlet and a war takes casualties. With the market dwindling in size according to many, a war it definitely is, and today's victories were the results of only a small battle, not the whole war itself.

Here is what I've come up with after retreating, counting my casualties, and bandaging the wounded. My results are a bit different to those you might find in other guides, but those guides have proven to be valuable sources of information, a base I've built my own guide on. The guys and gals that contributed to those guides deserve to be thanked. However, I didn't have much luck when it came to Intel, though I did approach them for support through the avenues available to anyone. Hard to reach up to, hard to get their ear, Intel really is this big goliath of a company, but I managed to get the necessary information through the help of other reviewers. Without direct help from Intel, I only had a limited number of samples to play with, which may have some parts to this guide not work with all CPUs.

What's New

Intel's latest platform makes a big change by using the new LGA 1150 socket. The socket uses less pins than previous sockets, but although there are less pins connecting the chip to the motherboard itself, the removal of pins isn't limiting functionality. Rather, the pins were removed because of a simplified power-delivery mechanism to the socket and because the main power regulation devices are now part of the chip itself. Board voltage regulation is still quite important, but rather than power quality being an issue with most value-oriented products, Intel's latest design has made it so that less expensive boards are just as capable as high-end enthusiast products when it comes time to clock your CPU. Those cheaper boards will still require more active cooling over the board VRM section, and perusing videos on YouTube by various reviewers and companies will re-iterate just that, with ASUS very plainly stating that their cheaper boards are exactly as described here: just as capable with better cooling.


That's not the only change the voltage regulation permutation brought about. Since voltage regulation for the chip's individual domains is on the chip itself, cooling required for Haswell-based CPUs has increased to a point where inexpensive but for their highly overclocked cooling performance favored coolers of past platforms aren't up to the same task with Haswell CPUs. The overall heat concentration of highly clocked Haswell chips is different due to the inclusion of the FIVR leading to very different thermal characteristics, which makes some of those $30 coolers that did great with Ivy Bridge completely useless to overclockers of Haswell platforms. Also, since the voltage sent into the chip is doled out to various parts right inside the chip, the controls offered are more complex than ever before, as are the chips and how you overclock them. The Core i7-4770K features far more flexibility than the older Core i7-3770K, with many more options in the BIOS helping you get the most out of your brand-new Haswell CPU.

One of the biggest changes comes in the form of available BCLK dividers. Intel's Haswell allows the BCLK of the chip itself to run at higher frequencies, although the same limits are still imposed by devices connected to the PCIe bus. The introduction of 125 MHz and 166 MHz BCLK dividers allows for much greater flexibility with memory and CPU overclocking, but PCIe devices are still part of the system, so only the same rough deviation of 15% from the base divider, either up or down, is possible. Buying a board with a PCIe slot connected to the Z87 PCH will give you greater flexibility because the base clock of the PCH always sits at the reference 100 MHz, eliminating problems with clock tolerances for PCIe devices connected to the Z87 PCH. Though most slots connected to the PCH only offer a PCIe x4 link, performance isn't affected enough to matter in memory overclocking, but it can have some impact in 3D testing. You can check out W1zzard's PCIe scaling tests using Ivy Bridge to get an idea of how PCIe scaling works HERE.

Haswell CPUs also introduce more memory multipliers (up to 2933 MHz) and more CPU multipliers (up to 80x). Another change is that the CPU's L3 cache speed is no longer derived from the CPU's speed, now featuring it's own multipliers which can auto-adjust to the workload. The iGPU portion of the chip has added flexibility too, but I don't have a lot to share on that specifically since most of us don't use it. The iGPU is much larger and has more horsepower than on past Ivy Bridge CPUs, so it can be a large source of heat, but I will address that in a moment.

In total, we've got a bigger iGPU, added dividers everywhere, and the power regulation. As evidenced by the larger TDP of the Haswell chips, all make for more heat, which has cooling change as well.

Cooling Considerations

I recently saw a YouTube video of an Intel rep stating that all of the chips since Sandy Bridge, including Ivy Bridge and Haswell, are 95W "Power Envelope" chips, and that although the TDP has changed between the high-end versions of these chips, the 95W figure has been part of each chip's design. This statement makes a lot of sense when we take into consideration that initial Core i7-3770K chips sold were marked as "95W" until people's complaints had Intel change the packaging to say "77W". It might also change how you look at these Haswell chips since both Ivy Bridge and Haswell are 95W "Power Envelope" designs on the same process but Haswell has way more functionality on a physically larger die, so its higher cooling requirement only makes sense. As simple as that sounds, it might not exactly be that simple because unlike older chips, the larger Haswell die is also offset from the center a bit, which makes the cooler's orientation even more important.


The design changes are pretty obvious on even a physical level once you remove the IHS on a Haswell chip. Once mounted into the socket, the CPU die sits parallel to the DIMM slots in most motherboards, so coolers with heatpipes might work best with the heatpipes lining up horizontally, not vertically (as you can see in my mock-up picture above). Our cooler reviewer, Crazyeyesreaper, is investigating this matter with his own Haswell test rig, so expect to hear him report about his findings in regards to this query soon. That said, the better performing of a cooler you can get for your Haswell CPU, the further you are able to push your chip. A fully customized water-cooling loop would be my personal recommendation for a decent long-term overclock.

One added consideration with the Haswell platform is VRM cooling, especially on mid-grade enthusiast boards and those products falling into the sub-$150 market. These boards often have their number of VRM input phases reduced, increasing the current each phase must handle, which increases temperatures. Heat is a major reason many high-end boards have seemingly overbuilt VRM sections—it's not about providing ALL that power but having each individual component operating as efficiently and with as little heat as possible, which makes sure no heat passes on to the CPU package by way of the board's PCB and CPU socket. Having so many different Z87-based motherboards here, from entry-level to the extreme high-end, I can tell you that a lot of different products share commonalities, but it's always easy to recognize the board's intended use by looking at the VRM section and its cooling. Boards with an "OC" focus usually have pretty basic cooling since liquid nitrogen vapors really take care of nearly all the heat. Other boards meant to push high clocks over the long-term have water-cooling integrated into their VRM-cooling solution instead. Those regular $200-or-so boards with relatively basic cooling...well, they might not overclock so well over the long term, and that's perhaps part of the upset we've seen in the past weeks from those that have bought into Haswell early. That's not true in all situations, but I'm confident that many of the issues people have with Haswell are directly related to the additional overall cooling required. That said, a lot of it is still just up to plain old Lady Luck and what you win in the silicon lottery.

The CPUs, What To Look For

A few specific things stand out when it comes time to look at the CPUs themselves, and which one to buy, even before you get your hands on one. First of all, there are two fully "unlocked" chips right now, the Core i5-4670K and Core i7-4770K. The i5 chip is a quad-core without Hyper-Threading, while the i7 includes Hyper-Threading. If silicon quality is the same, the i7 is more likely to produce more heat because of its pseudo cores. With heat proving to be a big factor in how you overclock, this might be the first time I recommend users consider the Core i5-4670K for a long-term overclock. The Core i7-4770K should be just as capable, but I cannot state how huge heat issues can be enough.

Speaking of heat and chips, Intel stated that these chips are more than happy to run near the throttle point, and that temperatures might not play a large role in chip degradation, but since the chip itself is larger, with greater functionality, tweaking every setting manually has become an important part of managing temperatures. When you do get your chip and boot into the BIOS, one of the very first things to check are the idle voltages. Write these values down or take a screenshot of the BIOS itself, now that so many boards offer screenshot capabilities directly in the BIOS. Here's what you want to look for in order of importance:

vCORE: The main voltage for the CPU cores. Stock values can vary from 0.95 V to 1.15 V.

vCACHE: The main voltage for the ringbus and L3 cache. Stock values can vary from 0.95 V to 1.15 V.

VCCSA: Contains the memory controller, the PCIe controller, and other I/O domains. This is the main System Agent's domain voltage. The stock value sits somewhere between 0.800 V to 0.950 V, with most seen so far sitting between 0.850 V and 0.900 V.

The next two voltages are different parts of the System Agent domain, separate from the main VCCSA voltage. There is not a lot of information on what these voltages are for, but they are, like the "VTT" value of past platforms, helpful when scaling up the BCLK.

VCCAIO: This is the analog I/O voltage. So far, stock values range from 1.000V to 1.050V.

VCCDIO: This is the digital I/O voltage. So far, stock values range from 1.000V to 1.050V.

The next voltage, VCC-in, is very important because all other voltages already listed are only relevant once it is considered.

VCC-in: This is the input voltage to the FIVR, which stands for "Fully Integrated Voltage Regulation". It can range from 1.650 V to 1.850 V at stock. Most chips I have had my hands on so far, and the chips of those I've spoken to, all seem to run at 1.750V while in the BIOS. A chip with a 1.75 V FIVR and stock CPU voltage of 1.025 V should OC a bit better than one with a 1.80 V FIVR and a stock CPU voltage of 1.025 V.


Once you have recorded those voltage values, or the voltage values you could get your hands on, as not every board monitors all voltages in the BIOS, you'll want to keep that piece of paper close because the voltages relate to one another in quite important ways. I will go into a bit more detail momentarily but want to cover the last item you need to pay attention to on your initial boot first—your CPU temperature in the BIOS. If your BIOS monitors CPU temperatures, jot yours down next to those voltages.