It’s not particularly difficult to assemble a PC. In the simplest case, you can get by with seven components: Case, power supply, mainboard, processor, processor cooler, memory module, SSD or hard disk plus a few cables. Afterwards, just like with a completely purchased PC, you still have to connect the keyboard, mouse, monitor, network, printer, power supply et cetera. When selecting and assembling PC components, however, there are pitfalls in the details: If you know them, you can avoid mistakes.
First read, then screw
Many mishaps happen because a function or assembly step is not well understood. Information helps against this: Read manuals carefully, research what you don’t understand using a search engine or watch videos, if necessary contact the manufacturer’s hotline. Don’t force fit what doesn’t fit right away.
Order helps: create sufficient space and bright lighting on the work surface, store screws and small parts clearly, photograph parts before disassembly (with a cell phone). Do not touch contacts on mainboards, PCIe cards and memory modules with bare fingers: On the one hand, skin grease, sweat and dirt particles interfere with the contact, on the other hand, electrostatic charges from your body can destroy sensitive components.
The most delicate components are processor sockets, especially those with over 1000 contact springs for pinless processors with contact surfaces, i.e. with a "Land Grid Array" (LGA). Many motherboard manufacturers refuse warranty if springs are bent or dirty. Apply thermal paste only when the processor is in the socket. A less than pea-sized blob of paste in the center of the processor’s sheet metal lid (called a heatspreader) is all that’s needed, it spreads by the cooler’s contact pressure. Some coolers have pre-applied paste and don’t need any more, others require you to peel off a protective film before putting them on.
Processor, cooler and RAM should be mounted on the mainboard before screwing it into the case: This way you can check the fit of the components. It helps to test fit the motherboard into the case without components beforehand: Fit the ATX I/O bezel as well as the threaded bolts under the board if necessary? And isn’t there one too many, which could possibly cause a short circuit??
Install the case fan, power supply and drives before inserting the mainboard, because a large CPU cooler blocks access to many screws. Put cables on the mainboard before you finally screw it down, then you can get to the connectors better. Before switching on, check once again if there isn’t a screw on the motherboard.
Connector: Pay attention to compatibility and polarity
A perennial problem: The PC doesn’t start because the ATX12V connector from the power supply isn’t plugged into the mainboard or the six- or eight-pin PCIe power cable to the graphics card is missing. Attention: ATX12V and (separable) EPS12V connectors are compatible to each other, but not to the PCIe power connector for graphics cards.
Difficult to recognize, but important is the polarity of the pin connectors for the PC power indicator (PWR LED) as well as the one that signals hard disk accesses (HDD LED). The 4-pin connector of the fan on the processor cooler should be connected to CPU_FAN – it also fits CHA_FAN for chassis fans or OPT_FAN (optional). The BIOS speed monitor may report errors if it does not detect a processor fan on the CPU_FAN. Also, the speed control depending on the CPU temperature works by default only on the CPU_FAN connector.
If your PC runs after assembly, but no picture appears on the monitor, check the HDMI or DisplayPort cable: it must be plugged into the graphics card, if present, and not into the mainboard. The Ryzens don’t contain a graphics processor, Intel’s LGA1151 chips do.
KISS principle: please not too complicated!
The most reliable component is the one that is not present, because then it can’t fail either. This is the quintessence of the concept, which is called "Keep it simple, Stupid" (KISS). According to this motto, we avoid noise at the source (quiet CPU cooler, quiet graphics card) in our PC building suggestions, instead of reducing it with an elaborate damping case, which can then cause problems with the cooling again – and so on.
With the power supply we pay attention to good efficiency at low load and do without exaggerated reserves, which minimizes losses. Low power consumption reduces not only power costs but also fan speeds and thus noise. In addition, we choose components that are as common as possible, are readily available and can be replaced by similar products if necessary. In case of doubt, we leave out onboard functions like WLAN or SPDIF output, which can easily be upgraded via USB, instead of choosing a more expensive motherboard, which might have disadvantages like higher power consumption or worse fan control. If possible we use proven components for several build proposals.
Finally, we don’t try to bring every component to the performance limit: Overclocking not only increases the waste heat, but also the risk of memory errors and sporadic crashes that are difficult to diagnose. We avoid more expensive products with special overclocking features that bring additional complexity to the device. That doesn’t mean you shouldn’t overclock – go ahead and overclock, but that’s on you.
BIOS setup and drivers
Current systems run with the default settings of the UEFI BIOS, i.e. with the "BIOS Setup Defaults". In many BIOS setups, the most economical and quiet operation possible requires adjustments to the CPU, PCIe and SATA saving functions as well as to the fan control characteristics. We regularly provide tips on this for our build suggestions for the optimal PC, most recently for the optimal PC 2021; we explained the fan behavior in more detail for the optimal PC 2018. Questions about BIOS updates are answered in our FAQ for the optimal PC 2021.
Install the operating system only after adjusting the BIOS setup. When it comes to Windows 10, you should build yourself a USB stick with the installation files of the respective current Windows 10 build, because many current drivers are in it, for example for the Intel network chip I219-V. After Windows 10 installation, start Windows Update manually, it often brings more driver (updates). For Ryzen systems, the AMD chipset driver is important. For Intel chipsets, Windows Update fetches good drivers automatically, as well as for the HD Graphics.
You should manually install Intel drivers for Rapid Storage Technology (RST), the sound driver (from the motherboard manufacturer) and, depending on the GPU, graphics drivers from AMD or Nvidia. After the installation, you can use the free benchmark Cinebench R15 to check whether the system brings the expected performance. The "Torture Test" built into the Prime95 search program puts the processor under full steam, where the fan control has to prove itself.
Warranty and guarantee
Something is more likely to go wrong with an individually configured computer than with a mass-produced off-the-shelf product manufactured thousands of times over – even if you only combine high-quality components. The most important factor for a reliable system is testing and experience. The latter are included in our PC building suggestions, but also here it can sometimes hook depending on hardware variant and firmware version of the individual parts.
In the case of complaints, there is a greater risk of problems with PCs that you assemble yourself than with complete computers: For the respective dealer – that is your contractual and contact partner in the case of complaints, not the manufacturer – it is tempting to shift the responsibility at first according to the motto: "The power supply unit must be to blame for the mainboard not working". If you don’t feel like doing that, it’s better to buy a complete PC or from a dealer who will assemble your desired configuration for you. We deliberately do not work with PC dealers on our construction proposals, so that no one interferes with us.
Be prepared to deal with missing or foreign-language documentation and a few mishaps – you should already have fun tinkering with the system! You’ll get to know your system and repair it more easily if something does fail. (ciw)