Assembling a Computer
While you can save a lot of money building a PC yourself, it?s important to take care in assembling it. Without following a certain precautions, you can wind up costing yourself in broken parts. In this document, I hope to be able to bring confidence to new system builders, and give some tips that might help those relatively new to PC building. Though it may seem daunting at first, assembling your own computer brings a sense of pride to using it, and knowledge of exactly what's inside. I'm going to assume that you've got your components picked out and purchased, and proceed directly to assembly.
These instructions are primarily for assembling a PC based on an ATX case, motherboard, and power supply. Older AT components assemble in a similar fashion. I will attempt to update this article when I am able to deal with some equipment based on the cutting-edge BTX specification. I strongly recommend that you read the entire article before beginning, and that you have some degree of PC hardware repair or upgrade experience before trying to build your own PC.
Preparation
The two biggest dangers in assembling a PC are static and debris. To protect from the former, you want to build your computer on a workbench over a hard floor. Walking on carpet can give you a static charge, which can damage components. You should also keep parts in their anti-static bags or containers until you're ready to use them. The other concern, debris, means simply that you want to keep your workspace and parts clean. Small bits of metal or packing material can cause problems, so take care not to introduce them to the assembly environment.
Now that we're done with the safety stuff, let?s get into the fun part. There is one major feature of your case that can affect the assembly process: a slide out motherboard tray. If you have one, make use of it, it makes assembly much easier to be able to do it outside the case. If your tray doesn't slide out, no worries; while the space is a bit cramped, you can still get the job done. In terms of tools for assembly, you should just need an average size Phillips screwdriver.
Step 1: Motherboard Insertion
Everything that you put in your system in some way connects to the motherboard. Thus, we insert it first. Motherboards attach to the case via a set of mounting holes on the board. Some of these holes should line up with brass standoffs on the motherboard tray. Key areas to have support under are the expansion slots and memory slots. If there are standoffs with no corresponding hole, remove them (they screw out) to prevent contact issues with the motherboard. If you're lacking standoffs in key areas, they can be added by drilling and tapping a hole in the tray (though this is difficult, and should usually be unnecessary). An alternative to this is the small plastic feet that ship with some motherboards and cases, which can be inserted into the mounting holes to provide support. At least a few holes need to be screwed in to provide secure mounting and some ground lines for the motherboard.
If your motherboard has an odd port layout, it may require a special I/O shield. This is the bit of metal that the ports poke through to the outside world. The motherboard should come with the shield if necessary (if it didn't, and your ports don't match the case, read on to special circumstances). Replacing the shield is a simple matter of popping the old one out and pressing the new one into place.
The motherboard should be slid into the case port-edge first. If you move it in at an angle, and line up the ports with the shield, you can then easily lower the motherboard down onto the standoffs. You may need to shift it a bit side to side to line up the holes. Once you're in, screw in the motherboard screws (usually short brass or steel screws with hexagonal Phillips heads) hand tight (There isn't a part of this project you should use a driver on; they can cause damage to the delicate threads involved). When the motherboard is in to your satisfaction, we can move on to the next step.
Step 2: Memory & Processor
The innards of computers are designed to optimize space and airflow, not to insure all components are accessible at all times. Because of this, it?s important to follow a certain order in installing components to make life easier (and prevent having to pull out stuff you've already added). The first component that we will add is the memory. All modern memory comes in the general form of a DIMM module. Modules are keyed so that they only fit in the slot one way, and will only fit in compatible slots. You want to fill slots starting with the largest module in the lowest numbered slot (there should be some indication on the motherboard or in the documentation as to which slot is slot 0). To insert a module, first press down the white tabs on the end of the slot, then press the module firmly and evenly into place. Some of the key patterns are nearly symmetrical, so if the module doesn't seem to go in at first, try flipping it around. As the module goes in, the tabs should swing up to clip it into place.
The next component to install is the processor. Because of their expense and fragility, modern CPUs are connected to the system through a ZIF, or Zero Insertion Force, socket. One corner of the CPU should be chamfered, or be indicated with a dot. This will match with a corresponding chamfer on the socket. Once you've found the appropriate orientation, you need to open the socket by pulled the locking lever out and up. The 'out' motion is really just a slight bend to unlatch the lever. The lever should lift to be perpendicular to the motherboard. Now that the socket is open, carefully set the processor on the socket. It should slide into the socket under its own weight. When it is properly seated, push the locking lever back into the locked position.
The heatsink is a critical component to keeping your PC running. The interface between the processor and the CPU is important. Some heatsinks, including most of the stock ones provided with boxed CPUs, come with thermal tape on the bottom. If your heatsink did not come with thermal tape, I would recommend applying a thermal compound to make a good thermal interface. Instructions for applying the compound should come with it, otherwise you can read below to special circumstances. The heatsink can attach to the computer in one of two ways. The first and more common method is by clipping to the processor socket. For some large, heavy heatsinks, you need to bolt them directly to mount points inside the case. Since mounting systems differ, and require that the motherboard be configured and drilled to accommodate them, I will leave installation of these to the instructions included with the part.
Before installing the heatsink, you may need to attach the fan if it is not already mounted. This is usually accomplished by screws on the corners of the fan or by wire clips along two edges. The best airflow direction for the heatsink fan is blowing down into the heatsink. Fan direction should be indicated by arrows on one side on the housing.
A heatsink clip is typically a bent metal strip that passes through the middle of the heatsink. The ends of this strip have holes to latch onto protrusions from the processor socket. The idea is to place the heatsink centered over the processor, and maneuver one end of the mounting bar to one of the protrusions. The best way to get the other end on is to pull out and down, pressing towards the protrusion on the other side of the socket. Typically, the mount points on one or both sides have a taper; it?s a good idea to make the second side one with a taper so that it?s easier to clip into place. Note that it takes a good deal of force to get the bracket to clip into place. You want to be careful to apply even pressure and to not shift the heatsink a lot while clipping the bracket into place.
Once the heatsink is in place, you want to connect the fan to power. The three typical ways this is accomplished is through a motherboard header (a thin 2 or 3 pin connector), a 3-pin bus connector, or a 4-pin drive power connector. Motherboard headers will be indicated on the motherboard. 3-pin connectors use either an adapter to connect to a drive power connector, or connect to a fanbus. 4-pin "molex" drive connectors can connect directly to a hard drive power connector. Since the last two connection options involve stringing a cable across the case, it may be easier to leave connecting it to later.
Step 3: Cables
The main cables that you want to get connected before adding expansion cards are the drive data cables and the motherboard power connector(s). The three drive cables that you may need to connect are the floppy cable, IDE cables, and SATA cables, depending on your drive configuration. The floppy cable is the narrower of the two ribbon cables that should have shipped with your motherboard, and has a twist in some leads before the last set of connectors. The floppy connector is usually labeled on the motherboard as such. You only need to have this cable in place if you're using a floppy drive (I recommend having one, as they're sometimes helpful, and cheap).
Most motherboards have two IDE channels, which support two devices each. Deciding on the layout of devices on these channels I will discuss later, for now you can assume that they will both be needed. Both the IDE and floppy ribbon cables are keyed to only connect one way; if the keying is not present, put the colored edge of the cable towards the pin indicated as pin 1 on the motherboard header. For SATA drives, you want one cable per drive connected to the motherboard SATA controller. If you're using a PCI card as an IDE or SATA controller, you don't need to connect those cables at this point.
Motherboard power is supplied through a large rectangular connector. It is keyed to connect to the motherboard only one way, and clips into place. On some Pentium 4 motherboards, an addition Pentium 4 power connector is required. This is a square 2x2 connector that connects to a corresponding, keyed, connector on the motherboard. If your motherboard requires this connector but your power supply does not provide it, there are adapters available to convert a hard drive power lead for this purpose.
Front panel connectors are what make your power and reset buttons work and the power and hdd lights glow. There should be a block of headers on the motherboard where all of these connect. This is usually one of the more poorly documented parts of the motherboard layout; usually you can find an indication of where in the header block the connectors go, though the direction is sometimes ambiguous. Since power and reset are momentary switches, polarity isn't tremendously important, but the power and hdd LEDs need to be connected the right way. Often, the only way to check is to move things around every time the computer is off until its right.
Step 4: Expansion Cards
Your graphics card usually requires the first slot, the AGP port. There may be a locking clip on the back edge of the port that you need to open before inserting the card. When inserting the card, press straight down with even pressure across the length of the card. It should slide all the way into the slot. Once the card is in, attach the mounting bracket to the case with one screw (if you have a tool-free case, there will be a slip to hold all of the expansion cards down. If this is the case, leave it open until we're done with all of the cards). Some high-performance video cards require that they be connected to a hard drive power connector. You should make that connection now.
The order in which PCI cards are added doesn't particularly matter, unless a specific part demands a specific slot. If you have room, it?s a good idea to leave the slot adjacent to the AGP port open for airflow reasons (some massive nVidia and 3dlabs cards actually fill both slots). PCI cards are inserted in the same way, straight down with even pressure. Use either mounting screws or the bracket on the case (if present) to secure the cards in place. Note that in front of all slots there will be a blank bracket or a pop out panel; keep the blank brackets for future use and carefully plan which pop out panels to remove.
Step 5: Drives
Drive mounting patterns vary by personal preference, but I like to space out my optical drives if possible starting from the top of the case down, and do the same with hard drives starting at the bottom of the internal bays. Drives mount to the cages either by screws or by mounting rails. Rails are easiest; you attack the rails to the drive outside the case and just push it into position from the front (for hard drives, this may require removing the faceplate of the case). If the drives need to screw in, you slide the drive in from the most convenient direction, lining it up as well as possible. You then insert 4 screws loosely (less screws are possible, but 4 is more secure. Especially difficult are screws on the back side of the case, which often require guiding through small access holes. After you've got all four screws in place, align the drive just right (especially important for the appearance of optical and floppy drives) and hand tighten.
One special case that can occur with hard drives is a lack of the 3.5" bays that they use. For this purpose, most drive manufacturers provide adapter rails to mount the drives in 5.25" bays (near the optical drives). I'd recommend doing this only if you need to, for reasons of wasted external bays, thermal problems, and cable run issues. You attach the adapters to the drives before inserting them into the case. Note that drive rails also work in this situation.
Now is when I will talk about the art of assigning drives to IDE channels. With the advent of SATA, this is becoming less of an issue, but most system builders will still benefit. Transfers between drives on the same IDE channel are slower than transfers between drives on separate channels. For this reason, optical drives should be split up to speed CD copying, and hard drives should be split up to speed things like video editing, which work better reading from one drive and writing to another. For this reason, I recommend the following layout:
Primary Channel:
-Master: Primary Hard Drive (OS, apps)
-Slave: Primary CD (fastest burner)
Secondary Channel:
-Master: Secondary Hard Drive (Data)
-Secondary CD (DVD, etc)
IDE connectors should be keyed to connect to the drive only one way; if not, the colored edge goes towards the power connector on the drive. The master connector on the IDE cable is the one at the end, the slave is the one in the middle. Drive power is supplied through 4-pin molex connectors (on IDE drives) or SATA power connectors (on SATA drives). Some SATA drives accept 4-pin molex connectors, though this disallows some of the power features of SATA, such as hot swapping. If your power supply doesn't have SATA connectors and your drive requires them, there are adaptors available (note that these also disallow special SATA power features). The floppy power connector is a smaller 4-pin connector, the widest edge of this faces down.
Step 6: Everything Else
Now is when we want to connect any case fans to power, and check that all other connectors are in place. It?s also a good time to route cables away from fans, for optimal airflow. This can be accomplished by running them in bundles with zip ties, though metal/paper twist-ties work as well. Before first power on, we want to put the side panel in place, and attach the keyboard, mouse, video, and power cables to the back of the computer. Leave the rest of the peripheral devices disconnected until the assembly has been confirmed to work. Before powering on for the first time, it?s a good idea to check anything that you're unsure of. At this point, a press of the power button should bring your new PC to life.
Step 7: It Didn't Start
It isn't uncommon for even an experienced system builder to forget an important connection that prevents the system from powering on. If your system doesn't start, unplug the power and check the following:
- Is the power switch connected to the right header? If you're sure it is, switch the polarity.
- Is motherboard power securely in place? The clip needs to be engaged.
- Are the memory and expansion cards all seated properly?
- If problems persist, additional help can be found here at Extreme Tech Support
With PCs, there are varying levels of 'turning on'. The most basic is that the fans and lights kick in when you press the power button. After this, there is a series of beeps that tell you how the most basic startup processes went. If things went mostly well, you'll get some startup messages on your monitor. If the machine fails to boot, there are various sites that list the beep codes from the major BIOS manufacturers (the BIOS is the part of the system that controls the beginning of the boot cycle and checks all components at power on. It can report problems with memory, expansion cards, and other things). Looking at these listings can at least give you an idea of where the problem is. If you can't resolve it yourself, there is always the forum to assist you. Be forewarned that there is a failure rate in computer parts, but most are warranted at least long enough for you to get them replaced if you are just adding them to your PC.
Once your new PC starts, you might need to make a few BIOS tweaks to make sure the right boot drive order is set, etc. Beyond that, its all OS and software install, which I'm sure will be covered at another time.
Special Circumstances
Sometimes, the parts of a PC just don't fit together quite right. You might need to insert some more motherboard standoffs, make your own I/O shield, or use thermal compound to ensure a good thermal connection between your CPU and heatsink. While this guide is in no way comprehensive, it should point you in the right direction.
Adding mount points for anything to a PC case is about the only time you're going to apply power tools outside actual case modding. Normally, adding new motherboard standoffs will involve moving an unused one to a new location, rather than adding to the existing standoff count (though you can purchase standoffs from some parts stores). You want to select the position of your new standoff by marking through one of the mount holes of your motherboard when it is aligned with the existing mount points. Once you've got the spot, clear all electronics from the area, and remove the power supply from the case (a metal shard in the power supply can cause hardware damage and even a fire). You want to drill a hole slightly smaller than the minor diameter of the threads on the standoff. You want to use a metal bit here if you have them, though wood bits at low speed will work as well. If you have an appropriate tap, tap the hole. Otherwise, this will just be a very tight fit (luckily, you almost never have to remove standoffs again). After drilling and tapping, you want to clear all chips from the area, and clean up the hole with a file. And debris left in the case from this process can be fatal to the system. You screw the standoff in with a hex driver, or some have a convenient slot for a screwdriver. You want these to be as tight as you can get them by hand; otherwise motherboard removal can be a pain.
If your motherboard doesn't match your current I/O shield, and didn't include a replacement, there are a few things that you can do. First, if the difference is minor, you can cut the existing shield with a pair of snips. If the port layouts are wildly different (this doesn't happen often) you might need to resort to getting a piece of high-gauge sheet metal and drilling/cutting it to fit. It is preferable to cut up the old shield, though. The key points are for every port to be touched by the shield, and for unused holes to be covered to prevent airflow and dust issues. The shield touching the ports allows for certain grounding properties. Duct tape works fine to cover unused holes. Remember than just an approximate fit is needed; this is the back of the PC, so beauty isn't a great issue.
Applying thermal compound is really a simple process. You want to put a BB size amount on the center of the processor (on the square part that sticks up, the 'core') and spread it evenly with some device (the end of a zip tie works well). It is important to not scratch the processor and to not get compound on areas other than the core. Once the compound is in place, you can attach the heatsink as normal. Generally good compounds to buy are from the Artic Silver line (a new version comes out every so often; I believe it?s around Arctic Silver 5 at the time of this writing). If you're not overclocking your machine, any compound will work really. The key is to get a thermal compound, not a thermal epoxy, as an epoxy will permanently bond your heatsink to your processor.
