re: Build the Best Gaming PC Your Money Can Buy: A Detailed Guide (Updated Sep 2014)

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++++ALERT: You are reading an out-of-date version of the guide and wasting your time. Read the PDF for the most accurate up-to-date info.It's best to download the PDF and use a proper PDF reader. Google's formatting of PDFs breaks all of the links. Link to directly download the PDF. I have stopped updating the text in the thread because the forum's limited code makes it far too time-consuming to change images and add text.++++
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====PCI Express (PCIe)====
The full name is Peripheral Component Interconnect Express. We’re going to call it PCIe. Wikipedia provides a geeky explanation of the interface, but for now, we’ll just focus on what it’s used for. PCIe interfaces with a variety of components that connect to your peripherals. It communicates with your chipset via “lanes.” A single lane consists of two pairs of wires/tracers. One pair of wires sends packets of data, and the other pair receives.

There are 4 bandwidth levels of PCIe, and they’re commonly known as x1, x4, x8, and x16. This indicates how many “lanes” have access to the PCIe slot. Technically, there is a different sized slot made for each of the 4, shown below:



Most motherboards are only going to have a combination of x1 and x16 slots. The x8 and x4 slots are rare to nonexistent these days. The reason for this is the x16 slots are physically compatible with cards that require 1, 4, 8, or 16 lanes.


A typical motherboard has a combination of PCIe x16, PCIe x1, and regular PCI slots. PCI slots are becoming more obsolete these days but are still used for various legacy needs, such as FireWire cards, and even some sound and Wi-Fi cards.

The x16 slot is of particular importance, because it holds your graphics card.

But it’s not enough to simply choose a motherboard based on the number and type of PCIe slots it has. The more important thing to consider is the number of lanes those slots share. There might be 16 lanes available for each PCIe x16 slot on a motherboard, but there are other factors at play that dictate exactly how many of those lanes can be used at once.

###PCIe Lanes and AMD###
In AMD motherboards, the number of usable lanes is determined by the chipset. AMD’s 990FX chipset provides access to a total of 38 PCIe 2.0 lanes. How they’re used depends on how many PCIe slots are being occupied. If you are running one graphics card, all 16 lanes of the slot will be used. If you add a second graphics card to an available x16 slot, that slot will also use all 16 lanes, for a total of 32 lanes—commonly referred to as an “x16/x16” configuration. Beyond that largely depends on the way the motherboard was made. If there are 3 PCIe x16 slots available, using three graphics cards will usually mean an x16/x8/x8 configuration.

The 970 chipset has 22 PCIe 2.0 lanes available. What this translates to is 16 lanes for a single graphics card, and the number of lanes for a second graphics card depends on the motherboard. The 970 standard only allows for an x16/x4 configuration, but motherboard manufacturers can include chips or switches that control the use and allocation of those lanes to allow for an x8/x8 configuration.

###PCIe Lanes and Intel###
In Intel motherboards, the CPU determines how many PCIe 3.0 lanes there are, and the chipset determines the number of PCIe 2.0 lanes. Intel’s Haswell and Ivy Bridge CPUs (e.g., 4670K, 3570K) allow 16 PCIe 3.0 lanes (and 4 PCIe 2.0 lanes in the Z series chipsets). A single card will get 16 lanes, and two cards would be in an x8/x8 configuration. Higher end Intel motherboards also contain chips that use an active switching function to effectively double the available PCIe lanes (synthetically, similar to the way hyperthreading works).

###Another Variable: PCIe 2.0 vs. 3.0###
While Intel has far fewer PCIe lanes at its disposal than the 990FX platform, there’s another variable at work here: PCIe revisions. Intel’s Ivy Bridge and Haswell CPUs support PCIe 3.0, and their respective Z chipsets support PCIe 2.0, so the Z87/Z77 motherboards use PCIe 3.0 slots for graphics cards and PCIe 2.0 lanes for everything else. AMD boards use PCIe 2.0 slots/lanes. PCIe lane speeds are measured in gigatransfers (GT/s), and PCIe 2.0 lanes have a transfer rate of 5 GT/s, while PCIe 3.0 lanes have a max rate of 8 GT/s.

###What Does this Mean?###
Right now, practically nothing. The cards on the market right now will fit in either slot, but they don’t saturate the full bandwidth of PCIe 2.0 x16, let alone PCIe 3.0. As it stands now, your single graphics card will perform the same on any of the platforms.

I would go into the technical details, but I’m assuming by now you’re willing to just take my word for it: If you were to add a second graphics card at some point, there would be no performance difference between PCIe 2.0 x16/x16 and PCIe x8/x8 except in the highest end graphics cards (such as Titans and dual-GPU cards), and only at resolutions exceeding 1440p. You would get a marginal performance gain (< 4%) at best moving from PCIe 2.0 x8/x8 to PCIe 3.0 x8/x8, and even less of a gain going from PCIe 3.0 x8/x8 to x16/x16 (available on Intel’s high-end socket 2011 platform). Ultimately, the 990FX chipset would have the slight advantage over Intel’s Haswell/Ivy Bridge due to extra lanes if you were going to use more than two graphics cards, but I have always subscribed to the notion that if you think you need more than two graphics cards at any point, it’s time to just upgrade to a more powerful single graphics card. The only situation that warrants three or four graphics cards are for extreme systems using the fastest GPUs available—systems that are likely to be using Intel’s enthusiast platform anyway.

Now, how long the difference will be negligible is up for debate. In single-card setups, which includes all three of our sample builds, it’s unlikely that it will matter anytime soon—not before you’re long overdue for a full platform upgrade, anyway.

Ultimately, I’d recommend a motherboard that supports a second graphics card*. For gaming performance, the most impactful upgrade will always be your GPU. People go through several graphics card upgrades without changing any other component in their system. Being able to simply buy another of the card you already have is convenient and cost-effective, and it’s only achievable with a motherboard that supports the second card (and a compatible power supply, which we’ll discuss in its appropriate section). A motherboard that fits this criterion should have 2 PCIe x16 slots that run in an x8/x8 or x16/x16 configuration. You can also use Crossfire in an x16/x4 configuration (but not SLI), with very slightly reduced performance but still effective.

*Note: Some motherboards only support Crossfire (AMD cards), and not SLI (NVIDIA). It’s important to read carefully if looking for a motherboard that supports both.