Installing the Power Supply
Hopefully, if you're building a high-end PC today, you're using a fully-modular power supply. We wouldn't recommend anything of the non-modular or semi-modular variety if you're spending more than $75 on a PSU (which you should when building a high-end PC, by the way). In the accompanying photo, we've labeled the key cables that just about any build will require, so that you can pull them out of the PSU parts box. Note that systems using only M.2 drives will not require any SATA power cables, which provides for a very clean build. We've included both M.2 and 2.5" drives in our build for illustration purposes. Another thing to note: depending on the video card you use, you may need to run dual PCIe power cables. This is vastly preferable to using the splitter that may come in the box with your video card. Our GeForce GTX 1070 card only required a single 8-pin power cable, so we've only pictured one in the photo here.
If you're using a case with a PSU shroud, you'll definitely want to connect all the necessary cables before inserting the PSU into the case. That's because reaching under the shroud to install modular cables is very challenging due to the limited working space. Make sure to fully insert each of these cables until the locking tab clicks in. Otherwise, you may find your system unable to boot once it's all come together, and you'll be left scratching your head as to what's wrong. Every build will require at least two cables: the 24-pin motherboard power cable, and the 4+4-pin CPU power cable. This CPU cable is split at the motherboard side because some basic motherboards only require a 4-pin connection, but all high-end boards will require that you join the two ends together to form a single 8-pin connector. As we mentioned, we also have a SATA power cable for our 2.5" solid-state drive, and a PCIe power cable for our GTX 1070 graphics card.
Now here's a step you might not see covered elsewhere, but it's an important one: screwing in the power supply. Unfortunately, we actually had a reader destroy a power supply by picking up a long screw (rather than the short screw that came with the power supply), and affixing the screw directly into a vent hole, damaging a capacitor inside the power supply and rendering the power supply inoperable. The power supply is designed to be inserted with the fan either up or down, depending on the internal layout of your case, and that's why it appears there are eight screw holes you can use to affix your power supply. In fact, there are only four you can use, and you should make doubly-sure you are using the right ones before you go screwing into a vent hole. Truth be told, we've made this mistake before, but luckily didn't damage any internal PSU components! We've highlighted the holes to be used to mount a PSU with the fan pointed down (as you'll do with most modern cases), and we've "X'd out" the locations that look like screw holes, but are in fact PSU vent holes that you want to avoid screwing into.
All right, as seen above, our power supply is now fully installed, and we've routed the cables so as to get them ready for motherboard installation. Note the 4+4-pin CPU cable is routed up to the rear corner of the case, while the 24-pin and PCIe power cables are routed to the center of the case. To keep things simple in this photo, we've removed the SSD.
Installing the Motherboard
Now it's time to drop in your motherboard, which will turn this shell of a PC into the real thing! Note that there are two steps you need to take before inserting the motherboard. First, slot the I/O panel into the back of the case. Hopefully, you're lucky enough to have a padded I/O cover, which higher-end boards like our sample MSI Z270 Gaming Pro Carbon come with. Otherwise you'll be stuck with a punched-metal panel that's a lot harder to install, and has all sorts of hanging bits of metal that can get in the way of ports. They never fail to block at least one USB or HDMI port, in our experience (and to our chagrin!).
The other step you need to take before dropping the board in is to confirm that the correct motherboard standoffs are installed in the case. Many cases, including the SilverStone model we used, only include six pre-installed standoffs. That's because some budget motherboards are narrower than the standard ATX spec and don't require the full complement of nine standoffs. We find that the easiest way to screw these posts in is actually to insert a screw into them, and affix the whole thing together, and then back the screw out once the post is in. You might need a pliers to accomplish this by the way. In the photo above, you can see that we're installing a new standoff in the top-right corner of the motherboard tray. With that out of the way, we'll drop the motherboard in and secure it to the standoffs. In the photo here, we've highlighted a screw in the middle of the board, as well as a screw on the right side of the board that's being affixed. Remember how on the first page of this guide, we recommended a magnetic-tip screwdriver? This is the step where you're going to be very thankful you have one. It makes reaching the screw holes at the top of the board a whole lot easier!
The next step is the one that will require some dexterity: attaching all the power and data cables to the board. This includes the 24-pin and 4+4-pin power cables that come from the power supply, the SATA data cable for any 2.5" or 3.5" data drives you're using, fan cables, as well as the assortment of cables that come from the front of the case (USB, audio, and power buttons and LEDs). In the photo above, we've highlighted all the smaller data cables you'll need to attach (with the exception of the USB 3.0 cable, which is up near the 24-pin power connector). Note that every motherboard manufacturer has a slightly different approach to how users should attach the front panel connectors. As it happens, MSI chooses to make it as difficult as possible, as there is no extra key insert that you can attach your cables to outside of the case, nor is there a silkscreened legend on the motherboard itself. You actually need to read the manual, shockingly. Our favorite attachment system is found in Gigabyte boards, followed closely by Asus and AsRock boards. In the photo below, we've highlighted the two power cables that must be connected for the system to boot. You'll want to make extra certain these are inserted all the way, because a half-inserted cable will not provide proper power.
Installing the Video Card
Believe it or not, we're almost done. Now comes the fun part: installing the beast of a video card that will turn this docile system into a true gaming powerhouse! Everything we've done so far would be relevant for a simple home office PC, by the way, and if that's what you're building, you can stop right here and load up your OS. But if you're actually building a gaming system, read on!
Installing the video card isn't too hard, but you'll want to make sure you drop it down straight into the PCIe slot to avoid any potential damage to the motherboard. It helps to have the case laying on its side here, so you can easily see what you're doing and have gravity help you, rather than hinder you. Then you'll affix the two PCIe slot screws that are pre-installed in the case (and which you removed when you pulled the slot covers out - you did do that, right?!?).
Now here's a step a lot of builders forget about: connecting the PCIe power cable to the video card. Yes, you do need this connected for your video card to work, and yes, you do need all of the pins filled. So if you have a 6-pin cable in your hand, but your video card requires an 8-pin cable, you'll need to dig through the cables that came with your power supply and find the correct one. The 6-pin standard is slowly giving way to the 8-pin standard, so what most current power supplies use is a split 6+2-pin cable that can be used for either arrangement. You'll see that highlighted in the accompanying photo here. You'll need to fit the two sides of this connector together and then insert it into the video card if you do indeed need 8 pins, as we do for the GTX 1070 we used.
Hey, guess what? The system's ready to run! In the photo below, this PC is fully cabled up, and all we need to do is plug our power supply into a power outlet and press the power button. It will start up first time, right?!?
Well, nine times out of ten, there'll be some minor snag a first-time (or 100th-time) builder will hit that keeps this system from running, so make sure to double-check all your power cables, your RAM, and your front panel connectors before pressing that power button to avoid any nasty surprises!