PCIe cable

Installing the Video Cards

So, as you've probably gathered by now, we're going to be installing two video cards in this system. We recommend, however, that you always set up and stability test your system with one card, and then once you have all your settings right and your applications loaded, you add the second card. There's just no reason to add in unnecessary complexity when installing the OS and programs.

If you've ever been in and out of a PC case, you've likely come across a video card, and most enthusiasts got their start in PC building by upgrading a video card somewhere along the line. So you're probably familiar with the power cables used to feed GPUs the power they need, but in case you're not, we've included a photo here of a standard 6+2-pin connector. Because video cards can use either 6- or 8-pin PCIe power inputs, all power supply manufacturers have settled on a split connector, which provides flexibility. Have a 6-pin card? Then use part of the connector. Have an 8-pin card? Then fit the two parts of the connector together and insert them as one into the video card. Have a model that requires both an 8-pin and a 6-pin, or one of the totally-insane models with dual 8-pin inputs? Then pull another cable through from your power supply. Note that you must fill all power inputs on a video card, even if you won't be overclocking, as video cards are designed to throw an error at bootup if an incorrect power configuration is detected.

Video Card

In the photo here, you can see our first card installed. The GeForce GTX 1070 and GTX 1080 are unique among ultra-high-end cards in recent memory in that they only require a single 8-pin connector, which can provide 150W of power in addition to the 75W supplied by the motherboard's PCIe slot. In the past, cards that needed this much power used two separate 6-pin connectors, each of which supplied 75W. This design was intended to allow users of legacy power supplies, which did not have 6+2-pin connectors, to power up their video cards easily. Now that all modern power supplies have the 6+2-pin connectors, it's good to see video cards finally using them! It makes cabling so much simpler.

As we mentioned, we'd advise that you stop here and get your system up and running, and then return later on to install your second video card. If you scroll down to the bottom of the page, you'll see our system fully built up, including our two GTX 1070 cards. Note that we used two Nvidia SLI connectors to boost the SLI bandwidth available for inter-card communication.

This is in fact the first time that using two cables actually increases performance. While we know plenty of builders thought that they could use both SLI fingers on previous-gen cards to boost speed, it actually didn't do anything at all. The two fingers were designed to allow for Tri-SLI setups. Ironically, Nvidia has now ended support for Tri-SLI in game drivers, and probably could have simply equipped its Pascal generation of video cards with one SLI finger, but realized there was another use for that second finger: alleviating the huge bottleneck that existed in an SLI system originally designed for much slower cards. While standard SLI operates at 400MHz, the new dual-link system allows for an 800MHz communication channel, and if you use Nvidia's High Bandwidth (HB) SLI bridge, it jumps to 2 x 650Mhz, or 1,300MHz. To configure SLI, you'll need to go into the Nvidia Control Panel and select "Maximize 3D Performance." It would be simpler if it just said "enable SLI," but perhaps Nvidia's just trying to get you pumped up for the performance to come!

SLI

Our HB SLI bridge didn't arrive in time for our publication of this article, but based on our initial testing, we've found that simply jumping from the one standard SLI bridge that comes with every SLI-certified motherboard to two standard bridges can provide a performance boost of 3-7%. That's nothing to sneeze at, especially when an extra SLI cable will cost you $7, a small price to pay versus the other tweaks you might spring for to squeeze every last bit of extra performance out of your ultra-high-end system. Need more convincing? Well, we plan on providing some benchmarks using one SLI bridge, two SLI bridges, and one HB SLI bridge in the near future!

Overclocking

We get asked about overclocking a lot, and the truth is that OC'ing is very much a game of chance. Sure, there's some skill involved, but ultimately your fate lies in the particular characteristics of the chips you have, and that means your CPU and GPUs. This has become increasingly true with modern CPUs and GPUs, which have a lot of fail-safe protections built in that limit high-voltage overclocking. So while we can't tell you for sure what speeds you'll hit or what voltage you'll need to hit them, we can give you a few pointers.

First, download the following four apps: CPU-z and HWMonitor for the CPU, which allow you to monitor temperature, voltage, and clock settings. Then download GPU-z and MSI Afterburner for the video cards, which allow you to view basic specifications and enable overclock settings, respectively.

Afterburner

We suggest you start with video card overclocking, which is simpler than CPU overclocking. AMD Radeon cards allow you to select a specific core and memory clock you want to try, while Nvidia cards use offsets, which make determining your target clocks a bit of a arithmetic challenge. Most cards released in 2016 (including the Radeon RX 470 and 480, along with the GeForce GTX 1060, 1070, and 1080) can be clocked about 10-15% over reference GPU clocks, and 5-15% on the video memory. If your card is pre-overclocked, your headroom will be partially used up already, so keep that in mind. GPU-z will help you determine what your card's out-of-the-box clocks are.

Here's a quick tip that will let you get a "free" overclock on any GeForce-based card: increase the power limit to the maximum in MSI Afterburner. It poses no risk to the GPU, will never lead to a single game crash or bluescreen, and will allow your GPU to run as close to its maximum boost level as possible. We've found that simply increasing the power limit allows GPUs to gain a 5% speed boost! The MSI Afterburner screenshot we include here is for an older GTX 980 Ti video card, so these exact settings don't apply, but it still gives you a sense of the tweaking options you have.

If you want to push futher, consider that none of the three Pascal-based cards we've sampled so far have been able to achieve anything more than a 10% overclock. So start slow, and set your expectations low, and maybe, just maybe, you won't be disappointed! For the record, our GTX 1070 Founders Edition could hit +190 over reference, while our EVGA GeForce GTX 1070 SC could only do +163 over reference, both with +1000MHz on the VRAM. While we didn't feature it in this guide, our GTX 1080 sample hit +159MHz over reference on the core and just +500Mhz on the VRAM. All three cards ran at clock speeds around 1975-2025MHz in game. While you may hear people boasting about hitting way over 2100MHz, we're betting that these overclocks don't actually hold while gaming (they just register for a split-second before Pascal's power-gating kicks in), and furthermore weren't stress-tested. We use 3DMark Fire Strike, specifically Graphics Test #2, to validate all of our overclocks. 3DMark Fire Strike will separate the men from the boys when it comes to OC'ing. We saw our Nvidia drivers crashing hard with seconds of running the test with an overclock that otherwise seemed stable in a handful of games.

CPU-Z

Once you're ready for CPU overclocking, check out Intel's Extreme Tuning Utility (XTU), which allows you to tweak CPU settings on the fly in the Windows environment. It unfortunately tries to do everything, so it has quite a busy interface, and you'll probably want to set your CPU overclock in your motherboard's UEFI eventually, but XTU will help you figure out what that should be. You'll also need some stress tests, and most CPU overclockers use either Prime95 or IntelBurnTest (IBT), but again XTU works here. Our personal preference is to use three separate applications simultanerously, one for setting the overclock, another for stressing the CPU, and a third for monitoring. IBT utilizes an AVX component that seriously stresses the CPU, as do newer versions of Prime95. The AVX load is so great, in fact, that Intel's board partners have included a negative AVX offset in their UEFIs for 2016. This offset is specifically designed to help overclock Broadwell-E chips, which may be able to hit some pretty high overclocks, but probably can't do so when AVX is in use. We recommend a negative 4 offset to keep things stable if you're going to either run AVX apps or an AVX-based stress test. This will take your CPU speed down 400MHz when an AVX load is detected.

We had read pretty bad things about Broadwell-E overclocking, but our guess is that a lot of the initial bad press was just that: bad press. You see, the press uses free engineering samples in their launch-day reviews, and in our experience, chips that come early off the assembly line just aren't as good as ones that arrive later. Tales of 4.1GHz overclocks had us nervous, but in the end, we were able to hit 4.2GHz with 1.25V, 4.3GHz with 1.3V, and 4.4GHz with a fairly substantial 1.35V, the latter using the -4 AVX offset we mentioned. We'll be using our 4.4GHz setting for benchmarks that will appear in later articles, but for an everyday overclock, we'll actually stick to 4.2GHz. That's because the 1.25V required to maintain that speed is a lot more tolerable for long-term use. It generates far less heat, and is well outside of the "danger zone" when it comes to potential damage to the CPU from high-voltage overclocks.

As for RAM overclocking, we recommend you keep things simple: just use the XMP profile, and stick to DDR4-2666 or DDR4-3200 RAM on the X99 platform (the Z170 platform is more flexible in this regard). That will allow you to use an even 100MHz motherboard strap. Speeds below 2666MHz aren't worthy of an ultra-high-end system (and don't cost less either), while speeds between 2666 and 3200 will cause some real hardship when it comes to setting up a solid overclock while also maintaining low idle power use. That's because they force a 125MHz motherboard strap. Finally, as far as we know, Broadwell-E really can't support memory speeds at 3400MHz and above, but you're welcome to try it if you wish. Just keep in mind you may have to manually de-tune your memory to get it to work with your system. Note that the RAM we used was actually a 4x8GB kit of DDR4-3000, 15-15-15-35, which we manually tuned to DDR4-3200, 16-16-16-36. It's just what we had on hand, but we'd recommend builders buy a DDR4-3200 kit straight away. By the way, don't feel bad about sticking to rated speeds: these are still overclocked settings! 

Sweet!

Conclusion

Things have never been more exciting in the ultra-high-end PC space. Not only do we have awesome new multi-core CPUs to play with, but Nvidia's Pascal generation of video cards is taking performance to new heights, despite unheard of levels of efficiency. And then there's the fact that there are all sorts of new ways to actually put this power to good use, including high-refresh-rate 1440p monitors, 4K G-Sync monitors, and of course VR headsets like the headline-grabbing Oculus Rift. With a dual-GPU system using Nvidia's latest offerings, you'll have no trouble maxing out your games regardless of your choice of monitor or headset.

We also think that modern case design, along with the advent of M.2-based SSDs, has made PCs a whole lot more beautiful. Yes, we know that sounds kind of funny, but check out the photo of our completed build, up and running.

This is a far cry from the ultra-high-end build we assembled just a year ago, which used a more traditional power supply setup and a huge array of hard drive cages. It may have performed well, but it just didn't look nearly as good. We're not ones to shy away from critiquing our own work, so we've included a small photo below of last year's build (click it to get a better look). Gosh, it really was kind of gnarly-looking inside. How embarrassing!

Yuck!

And that's why we think it's really important that neither PC builders nor PC component manufacturers dwell on the past, because there's always more innovation to be had. On the computational side, this is left to the tech titans Intel and Nvidia, and in the SSD world it's all about Samsung, but there's plenty that smaller players can do to make PCs a whole lot more impressive in terms of noise, thermals, and aesthetics. And ultimately, to builders who take pride in their systems, these factors are just as important as raw speed. So while Intel, Nvidia, and Samsung surely help us to achieve the levels of gaming performance we yearn for, it's the likes of Corsair, SilverStone, EVGA, and Asus who make things really interesting and inspire us to keep coming back for another bite at the PC building apple!

We hope you've enjoyed your read through this hands-on guide. If you'd like to read more of our hands-on articles, flip over to our How-To Guides page. If you're ready to order up some parts to build your very own ultra-high-end PC, visit our PC Build Comparison Page for all the best options at every price point, updated monthly!

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