The best thing about being a PC enthusiastbeyond, of course, the never ending joy of serving as the personal support technician for friends and familyis being able to assemble a system from the ground up with the perfect mix of components for a given budget. That mix of components will vary depending on your needs, but with today’s market so rich with high-performance hardware at affordable prices, it’s easy to spec a custom system that will blow the doors off pre-built boxes from major PC vendors.
For those who lack the expertise to pick the best available components, we compile regular system guides outlining our recommendations at various price points. These guides are a great starting point for seasoned PC hobbyists contemplating a new build, but they’re an invaluable resource for less savvy users seeking guidance as they step into the enthusiast realm.
Users new to building systems from scratch need more than just a shopping list, though. There’s an art to assembling a rig from bare components. Building a PC can be a daunting task for a newbie who has never put a system together before. For those folks, we’ve crafted a step-by-step guide covering the basics of system assembly. Keep reading as we show you how to build a PC from scratch.
Before diving into assembly, you’ll want to gather a few supplies and find a large, clean work area that preferably isn’t teeming with static electricity. As far as tools are concerned, you shouldn’t need more than a Philips head screwdriver; one that holds screws in place with a magnetic tip is ideal. We’ll also be using rubbing alcohol, Q-Tips, and zip ties. Everything else that you need should be included with the various components you’ve gathered to put into the system. Yes, you’ll need those components, too.
Prior to removing any of the components from their packaging, you’ll want to take the precaution of grounding yourself by touching a large, metal object like a table base, filing cabinet, or your PC’s casewhatever’s nearbyin order to discharge any static electricity you may be carrying with you. Static electricity can be harmful to PC components. Some folks prefer to use an anti-static wristband in order to keep themselves grounded.
Assembling the core
The CPU lies at the core of the modern PC, making it an appropriate place to start our build. For this first step, you’ll of course want the processor, and also your system-to-be’s motherboard.
This particular assembly guide features an Intel processor with a LGA775 socket, so certain steps won’t be applicable to systems using AMD processors based on Socket AM2. Socket AM2 isn’t hard to figure out, though; processor installation instructions typically come bundled with both the processor and the motherboard.
After laying the motherboard out on a clean work surface, remove the plastic cover that shields the LGA775 socket’s pins from harm. Be careful not to bend or otherwise disturb these pinsthey need to line up just right with contact points on the base of the CPU.
With the plastic guard removed, you’ll easily be able to unclip the lever that holds the socket’s CPU retention mechanism in place. Flip this retention bracket back on its hinges to expose the socket in full.
Modern CPUs are keyed to ensure that they can only be inserted into a socket one way, just like a puzzle piece, so you should have no problem dropping your processor into the socket. LGA775 processors, for example, have little indents along opposing edges that line up with protrusions in the socket. If your CPU struggles to slide smoothly into the socket, chances are you’ve got it oriented the wrong way.
Once the processor is sitting comfortably in the socket, flip the retention bracket back down and use the lever to clamp it into place. This secures the CPU to the motherboard.
With the processor installed, we can move onto the application of thermal compound. Some folks like to apply thermal paste before dropping the processor into the motherboard, but I find that tends to be a little messier without making things any easier.
Before slathering thermal compound all over our processor’s exposed cap, it helps to make sure that cap is nice and clean. Gently brush the cap with a Q-Tip dipped in rubbing alcohol to rid it of any dust or oils that it may have picked up from your
grubby carefully manicured fingers during the installation process.
Next, we apply thermal compound. Most retail processors that come packaged with coolers will already have thermal compound applied to the base of the heatsink. If yours does, you can skip this step and proceed directly to heatsink installation. However, we recommend applying thermal compound yourself. Thermal compound works best as a very thin layer between the CPU and heatsink, and most heatsinks that come with paste pre-applied use a thicker layer than is optimal.
You really only need a small dab of thermal compound to ensure complete coverage for the CPU. The dollop pictured above is more than enough, and it’s best squeezed onto the center of the processor’s metal cap.
Next, spread the thermal compound over the processor, ensuring complete and even coverage. Some thermal compounds come with plastic spreaders, but you can also use a credit card or even a finger wrapped in a plastic bag. What you want to end up with here is a relatively smooth layer that’s just thick enough to completely cover the processor.
Don’t worry about getting a little paste on the CPU retention bracket; it won’t do any harm there. You will want to clean up any compound that makes its way onto the motherboard or its surface-mounted components, though. A Q-Tip dipped in rubbing alcohol should do the trick.
Once the processor is glazed with compound, we can turn our attention to the heatsink. If you’ve elected to do your own thermal compound application, you’ll want to make sure that the heatsink’s base is scrubbed clean. Rubbing alcohol usually gets the job done, but some heatsinks are slathered with particularly gooey, clingy, or otherwise uncooperative thermal interface materials. It may be necessary to break out more noxious substances, such as nail polish remover, to restore the base of the heatsink to a bare metal shine.
Be careful not to mar the base of the heatsink when removing any thermal compound that may cover it. Some heatsinks need to be scraped clean of thermal compound, and it’s best to scrape with something plastic rather than a metal tool that will gouge the heatsink’s surface.
With our system’s processor blanketed by a thin veil of thermal compound and our heatsink’s base scrubbed clean, it’s time to mate the two together. Before dropping the heatsink into place, ensure that all four of the heatsink’s plastic retention posts are rotated clockwise into their installation position. Next, place the heatsink on top of the CPU, lining up the four retention posts with corresponding holes in the motherboard.
When the posts are lined up, depress the black plastic tabs one by one to lock the heatsink into place. You should hear an audible click as each post locks into place.
Since the area around a modern motherboard’s CPU socket is often crowded with tall capacitors, heatsinks, and elaborate heatpipe arrays, I find it’s best to depress the retention post that’s least accessible first. The post directly opposite that one should be next, followed by the remaining two in whichever order you desire.
After locking the heatsink into place, plug its fan into the appropriate header on the motherboard. The CPU fan header is usually right next to the socket, but if you can’t find it, your motherboard manual should have a map highlighting its location.
Note whether the heatsink you’re using features a fan with a three- or four-pin header. That information will come in handy when we jump into the BIOS to configure fan speed control, since some motherboards can’t auto-detect fan types.
Since it’s a lot harder to work on a motherboard when it’s sitting inside a case, we might as well install the memory before we slip the mobo into our enclosure. These days, most systems run their memory in dual-channel configurations using pairs of memory modules. Motherboards are typically equipped with four DIMM slots, two of which correspond to each memory channel, so you’ll want to check your motherboard’s manual to determine which slots correspond to which memory channel. Be sure to install at least one memory module per channel.
Once you’ve figured out which slots to populate, sliding memory modules into place is a snap. Like processors, modules are keyed so they only fit into DIMM slots one way. Orient your modules accordingly, and apply even pressure along their top edge to seat them into the DIMM slots. If the module rocks back and forth as if on a central pivot point, you’ve got it turned around the wrong way.
If you’re running fancy-pants memory modules with ginormous heat spreaders, like those pictured above, you may run into clearance issues with larger aftermarket processor heatsinks. Unless the heatsink’s orientation can be changed to provide additional clearance for the DIMM slots, you’ll have to settle for lower profile memory modules or a less extravagant CPU cooler.
When memory modules are seated correctly, retention tabs located at the ends of the DIMM slots should swing up into their upright and locked position, ready for take-off. If these tabs aren’t completely locked, you should be able to flick them into place easily with your finger.
Preparing the enclosure
We’re done with the motherboard for the moment, and must now prepare the enclosure for its arrival. Time to break out the screwdriver, folks.
The first thing we need to do is remove the enclosure’s side panels. With some cases, only the left panel needs to be removed or even can be removed. However, if your enclosure has removable panels on both sides, we recommend taking both off. The additional access will come in handy when we clean up wiring within the case.
Most modern enclosures hold their side panels in place with thumbscrews or mechanical latches, so you probably won’t even need a screwdriver to remove them. And if you need instructions on how to use a screwdriver, well, perhaps assembling a system from scratch is a little ambitious.
Removing the case panels gives us access to the enclosure’s internalsmost importantly, the panel on which the motherboard will set. The motherboard doesn’t rest directly on the metal panel, though; that would create all sorts of short circuits. Instead, the motherboard sits atop a series of posts that separate it from the case.
Motherboard posts should come bundled with your case, and they can be screwed directly into the motherboard tray with your bare hands. Making sure they’re tight.
When screwing posts into the motherboard, be sure that they line up with the board’s mounting holes; posts that don’t line up can make contact with solder points on the underside of the board, creating short circuits. We recommend using at least six mounting posts for a standard ATX motherboard, but to be on the safe side, you might as well use as many as there are mounting holes on your board.
Once the posts are in place, fish the I/O shield out of your motherboard box. Most cases already come with a generic I/O shield, but chances are it won’t line up properly with your motherboard’s port cluster. If your case has a generic shield, pop it out and toss it. The I/O shield that comes with your motherboard should easily snap into place.
Before moving on, we’re going to save ourselves some hassle by bending back the metal tabs on the inside of the I/O shield. In the picture above, these tabs can be seen above the PS/2, Ethernet, and Firewire ports. Bending these tabs back will ensure that they don’t catch on the motherboard ports when we slide it into the system.
We’re now all set up to install the motherboard into the case, but before doing that, it’s worth filling in a few other components that will be easier to install in an otherwise empty enclosure.
First among these is our system’s hard drive. These days, it seems every case manufacturer mounts hard drives slightly differently, but the enclosure we’ve busted out today takes a simple approach. Hard drives slide neatly into internal 3.5″ bayswith the drive ports facing out, of courseand are held in place by screws. Depending on your enclosure, you may need to secure the drive with screws on both sides; it’s a good thing we removed the right-side case panel.
Which internal drive bay ends up housing the system’s hard drive is up to you, but I prefer to have drives sitting in lower rather than higher bays. Heat rises, and we might as well put the drive in the coolest part of the case that we can. If you’re running a system with multiple hard drives, try not to stack them in bays directly on top of one another. If possible, leave an empty bay between drives to allow air to flow freely between them.
Next up is our system’s optical drive. This goes in one of our enclosure’s external 5.25″ bays, and in traditional cases, it’s held in place by screws. Of course, these screws are slightly different from the ones that hold the hard drive in placeyou know, because it would be entirely too convenient for the same screw type to be used throughout. All the screws you need should come with the case, and as a rule, ones with finer threads are used to secure optical drives and the motherboard, those with coarser threads and small heads secure hard drives, and those with coarse threads and large heads are reserved for case panels and expansion cards.
If you’re going to be running a single optical drive, check to make sure that its jumper is set to Master or Single Drive. This should be the drive’s default position, and you don’t need to change it unless you plan on running a second optical drive off the same cable. Drives with SATA interfaces are a little more convenient, since they don’t have these jumpers and won’t need to be configured in this way.
You’ll notice that we’re installing the optical drive in the case’s highest 5.25″ drive bay. Optical drives aren’t used frequently, so we’re not so concerned with whether they’re in the coolest possible bay. Instead, I like to mount optical drives as high as possible in tower enclosures to make them easier to reach when the case is sitting on the floor.
If you want to kick it old-school, now would be the time to install a floppy drive in one of the enclosure’s external 3.5″ bays. Same drill as with the optical drive, except with fewer choices; most cases only have one, maybe two external 3.5″ bays. Those inclined to join the 21st century will probably have replaced the aging floppy drive with a zillion-in-one media card reader that slides into the same slot.
In goes the motherboard
With the case prepped and drives installed, it’s time for our populated motherboard to join the mix.
Standard enclosures are usually a little tight, so it’s easier if you insert the motherboard at an angle, port-side first. Line up the port cluster with corresponding holes in the I/O shield and gently set the board down on the mounting posts you screwed into the case earlier. If the motherboard is positioned correctly, its mounting holes should line up exactly with the posts below.
From here, you’ll want to screw the motherboard into place using screws provided with the case. When tightened, the screws should be snug, but there’s no reason to really torque on them.
Next, we tackle the case’s front-panel connectors for the power and reset switches, power and hard drive activity lights, and the PC speaker. Each motherboard lays these connectors out in a slightly different fashion, so you’ll have to consult the manual to determine which connectors plug in where. For hard drive and power LEDs, colored wires should be plugged into the positive pins on the motherboard.
It’s ridiculous that the industry hasn’t agreed to a standard for front-panel connectors that would eliminate the need to connect a mess of wires individually, but this is the system we’re stuck with. Be sure to plug in the front-panel connectors now, because things only get more crowded inside the enclosure from here.
While we’re connecting front-panel hardware, it’s worth tackling expansion ports. Most enclosures now come with front-mounted USB ports that hook into headers located on the motherboard. Depending on your case, these front-mounted USB ports may be tied to a series of wires that have to be connected individually, or they may connect with consolidated blocks that can be plugged in all at once. Obviously, the latter is much easier to deal with. If your case’s front-panel USB ports are attached to individual wires, you’ll need to consult your motherboard manual for a diagram illustrating how those wires should be connected to pins on the motherboard.
We’ve only addressed USB headers here, but the same applies for front panel Firewire, eSATA, and even audio ports. The wires for each front-panel connector should be clearly labeled, either on the wires themselves or in the manual that comes with your case. Your motherboard’s manual should have full pin diagrams for all its onboard headers that illustrate how these leads should be connected, as well.
Expansion cards join the party
There are only a few pieces we need to put into place to complete our build, and next up, we have expansion cards. Most systems will require at least one expansion cardgraphics, of coursebut some folks may also have a discrete audio card, TV tuner, or other auxiliary hardware to complement their motherboards’ integrated peripherals.
Before installing expansion cards, we need to make some room for them in the case’s back plate panel. Our screwdriver comes out again, this time to remove back plates corresponding to the slots in which we intend to install our expansion cards. Keep in mind that for most double-wide graphics cards, you’ll need to remove two PCI back platesone across from the expansion slot and a second back plate immediately to the left.
To seat an expansion card, place it into an appropriate expansion slot and apply even pressure along the top edge of the card until it slides into place. When properly installed, the card’s back plate should line up flush with the enclosure. Now use the same screws that held the case’s empty back plates in place to secure the expansion card to the case.
The expansion card installation process is the same whether you’re putting in a graphics card, audio card, or any sort of other peripheral. Just make sure that you’re using the correct type of slot, be it PCI, PCI Express, or with older systems, AGP. Like most PC components, cards are keyed only to fit into a slot one way, so you shouldn’t have a problem.
You’ll note that in the picture above, we’re installing the system’s sound card in the lowest expansion slot. At the very least, you should avoid putting expansion cards right next to your graphics carddoing so can impede airflow to the graphics cooler. I tend to put other expansion cards into the lowest slots to give the graphics cooler as much room to breathe as possible.
With the exception of the power supply, which we’ll tackle in a moment, we now have all the hardware installed in our case. Cabling comes next.
If your case has three-pin power connectors for its cooling fans, you can plug them directly into the motherboard. With some boards, this will even get you temperature-based fan speed control. The motherboard manual should map out all onboard fan header locations.
Cases that use fans with four-pin molex power connectors can’t be hooked into the motherboard. Instead, these fans need to be plugged directly into the power supply, which we’ll install in just a second.
First, we have a couple of other cables to connect, starting with the one for our optical drive. Depending on the drive, this cable with either be of the IDE or Serial ATA variety. The cable itself should come with your motherboard, and like most PC connectors, it’s keyed such that it can only be attached the right way.
Next, connect the hard drive with a Serial ATA cable from your motherboard box. The L-shaped connector only works one way, so you should be able to figure it out.
SATA cables are much thinner and more flexible than IDE ribbons, making it easier to keep cabling out of the way of other components. We’ll tidy things up a little later, so don’t worry about being too neat just yet.
The last piece of the puzzle to fall into place is our system’s power supply.
Depending on your case, the PSU may slide in from the back or from the side, and you may or may not have to attach a mounting bracket before it’s installed. PSUs feature an asymmetrical screw pattern at the rear to ensure that they’re installed in the correct orientation. Line up the screw holes in the power supply with those on the case’s rear panel before sliding the PSU into place.
Once the PSU is installed, toss the mess of wires connected to it over the side of the case. This will make running power cables to our components much easier, and we won’t need to use all of the PSU’s leads anyway.
If you’re running a power supply with modular cables, you only need to connect as many cables as needed for the hardware in your system. It’s usually easier to connect these cables before dropping the power supply into the system, if only because the area around the PSU can get a little tight in some cases, making it more difficult to plug them in later.
With the power supply securely affixed inside the case, it’s time to start our plug fest. First, attach the 24-pin primary power connector to the motherboard. Some PSU primary power connectors can be configured for both 20- and 24-pin motherboards, so make sure you’re using the correct setup.
Next, plug the auxiliary 12V connector into the motherboard. Depending on your PSU and motherboard, this will either be a four- or eight-pin connector. We’ve had a few readers mistake their PSU’s four-pin floppy connector for the 12V plug, so you’ll want to make sure you have the right one. The 12V plug is a chunky connector that looks like a smaller version of the primary 24-pin plug with fewer pins. As has been the case throughout this build, all connectors should be keyed to fit only one way.
Most modern graphics cards need a little extra juice, so we’ll plug them in next. Graphics cards typically use six-pin PCI Express power connectors, although some recent high-end models require eight-pin power.
If your power supply doesn’t have the right connectors for your graphics card, check the bundle of cables that came with the graphics card. Power adapters are typically included with retail graphics cards for those running older PSUs that lack PCIe power plugs.
With our graphics cards hooked up, we turn our attention to hard drive power. Serial ATA drives have their own type of power connector, another L-shaped plug that can only be inserted one way.
Some Serial ATA hard drives also have a standard four-pin molex power connector. You can use this connector in lieu of the SATA power connector, if you wish. However, don’t plug in both; that can damage the drive.
Finally, we plug in our optical drive using a standard four-pin molex plug. SATA optical drives may use a SATA power connector. Now would be the time to plug in any four-pin case fans, as well.
By now, the inside of your case probably looks like a tangled mess of wires, some of which are likely still hanging over the edge. The mess not only looks bad, but it can also impede airflow around important system components. We should really tidy the mess up with a little help from a fistful of zip ties.
First, gather any unused power supply leads into a neat bundle and zip tie them together. This bundle can be stuffed out of the way into your case’s empty 5.25″ drive bays. Empty 5.25″ drive bays make a good dumping ground for excess cabling because they generally don’t have venting or fans that might otherwise be obscured by a clump of wires.
With excess power supply leads out of the way, we can turn our attention to the cables we’re actually using. There are a number of ways to deal with these, depending on just how clean you want the inside of your case to look. We won’t go overboard here, but it’s worth taking the time to remove any slack in the cables and carefully route them along the case’s internal structure. Most cases have loops or cutouts that can serve as anchor points for zip ties, making it much easier to snake cables out of the way.
Your case’s internals don’t have to be immaculate when you’re finished, but you shouldn’t have cables impeding airflow around any components or case fans, or around case vents. Cleaning up internal cabling also makes it easier to work on the system later on, either to swap out components or add new ones when your brand-new system becomes hopelessly out of date after just a few short months.
We’re finished with the hardware now, so you can put the case panels back on, stand the case up, and start connecting peripherals like your monitor, keyboard, and mouse. Now would be a good time to plug in the power cord, as well, and to make sure that the power supply is switched to its on position. Hit the case’s power switch, and the system should spring to life.
Leaving the hardware behind
Software setup is far too broad for the scope of this build guide. However, before we leave you at the mercy of your operating system installation, there are a few loose ends we need to tie up in the BIOS. With most motherboards, you can get into the BIOS by hitting the Delete key right after the system powers on.
Each motherboard’s BIOS interface is a little different, but most follow the same basic conventions. If you’re new to building PCs, you don’t want to spend too much time poking around. If you’re not careful, changing some settings can actually harm system components.
The first thing we want to do in the BIOS is check to make sure that our processor’s power management features are enabled. These features will have to be invoked by the operating system, but if they’re not enabled in the BIOS first, they won’t work.
In systems with Intel processors, thumb through the BIOS menus looking for SpeedStep and the C1E Enhanced Halt State, both of which should be enabled or set to auto. With AMD CPUs, look to enable an option called Cool’n’Quiet. These CPU-specific power management features will likely be found in BIOS sections pertaining to advanced features or power management. Some BIOSes will keep them in a general tuning section.
Next, check to make sure that the BIOS has set the correct clock speeds for the front-side bus and memory. Clock speed control is usually found in an overclocking section of the BIOS, and you don’t want to mess with it unless you know what you’re doing.
Overclocking instruction is well beyond the scope of this guide, and we wouldn’t recommend running your first custom system build at higher-than-stock speeds, anywayat least not for a while.
Once you’ve confirmed your system’s clock speeds, find the BIOS’s memory timing controls. Your memory modules will be rated for specific latency timings at a given clock speed. The BIOS should detect these defaults automatically, but if it doesn’t, you can set them manually. Just be sure that the memory timing settings that you use correspond to the capabilities of your memory modules.
Depending on your DIMMs, you may also need to raise the motherboard’s memory voltage. This setting will most likely be found in an overclocking menu, usually as the DRAM voltage. Be sure to set this voltage only as high as is required by your memory modules.
The final element of the BIOS we need to touch on is fan speed control. Options vary considerably from motherboard to motherboard, but you want to make sure that automatic fan speed control, often referred to as “smart fan,” is enabled if it’s an option. You may also see a fan option asking whether you’re using a three- or four-pin fan, sometimes referred to as DC and PWM, respectively. Select the appropriate fan type based on your processor cooler type.
If you’re lucky enough to have a BIOS that provides extensive fan speed control, take this time to explore the fan speed options. The defaults are usually adequate, but you may want to revisit them later if you find your system running too hot or too loud for your tastes.
Welcome to your new PC
Congratulations, you’ve just assembled a PC from scratch. Hopefully the process was relatively pain-free, and we’ve been able to give you some additional insight that you won’t find in the instructions that came with your system’s various components.
If you did run into any snags, the first place to go for help is our System Builders Anonymous forum, where you can pick up build tips and troubleshooting help from our community of PC enthusiasts.
Of course, there are numerous ways to tackle system assembly and different paths from bare components to a functional rig. We’ve presented our preferences, but they’re by no means the only way to do things. Enthusiasts have plenty of choices and flexibility when it comes time to build a system, and we couldn’t be happier about that fact.