Building a PC step by step: order, precautions and checks

Building a computer doesn't require special skills, but it does require order. Almost all the problems I see in home-built PCs come from a skipped step or one done in the wrong sequence: a forgotten standoff, a connector not pushed all the way in, a cable blocking a fan. This is the sequence I follow and recommend.

Before you start

Check compatibility

Before buying, check that:

• processor and motherboard share the same socket and the BIOS supports that processor;
• the memory is the right type (DDR4 or DDR5) and desktop form factor;
• the motherboard fits in the case and the graphics card fits lengthwise;
• the cooler isn't taller than the case allows and doesn't cover the RAM slots;
• the power supply has enough wattage and connectors.

Prepare the workbench

You need a large, well-lit, non-carpeted surface, a medium magnetic Phillips screwdriver, cable ties and a bowl for screws. Keep the motherboard manual close at hand: it's the most important document of the whole build. Before touching components, discharge yourself by touching a grounded metal surface or use an antistatic wrist strap.

Phase 1: assembly outside the case

Working with the motherboard resting on its box is much easier than doing it inside the case.

1. Processor: lift the socket lever, line up the small triangle on the CPU corner with the one on the socket and set the processor down without forcing it. Lower the lever. Don't touch the contacts or pins.
2. M.2 SSD: remove the slot heatsink if present, insert the drive at an angle, press it down and secure it with the screw or latch. Peel the film off the thermal pad before refitting the heatsink.
3. Memory: open the latches, insert the modules in the slots the manual indicates for dual channel and press firmly until the latches click.
4. Cooler: fit the brackets according to the instructions. If thermal paste isn't pre-applied, put a small amount in the centre of the processor. Tighten the screws in a cross pattern, a little at a time, to spread the pressure.

Phase 2: prepare the case

• Fit the power supply, usually at the bottom with the fan facing the lower filter if the case has an opening.
• Check the standoffs: they must match the motherboard holes. An extra standoff where there's no hole can cause a short circuit.
• If the motherboard doesn't have an integrated rear I/O shield, fit it into the case now: it's the step people forget most often.

Phase 3: motherboard into the case

Insert the board at an angle so the ports go into the I/O shield, rest it on the standoffs and secure it with all the screws without overtightening.

Phase 4: connections

Connect in this order:

1. the motherboard's 24-pin power;
2. the processor power 8-pin (or 4+4) at the top left, often the hardest to reach: if the case is tight, route it before fitting the cooler;
3. the cooler and case fans to the indicated headers;
4. the front panel: power button, LEDs, audio and USB. The manual shows the pin layout; double-check the small connectors;
5. the graphics card in the main PCIe slot, screwed to the case, with its power cables fully seated;
6. any SATA drives, with data and power cables.

Phase 5: first boot

Before closing the case:

• make sure no cable touches the fans;
• connect the monitor to the graphics card if there is a dedicated one, not to the motherboard;
• switch on the power supply and press the button.

The first boot may take longer than expected, because the motherboard performs memory training. On DDR5 platforms it can last a few minutes with a black screen: don't switch off straight away. Many boards have diagnostic LEDs that show whether the hang relates to the processor, memory, video or boot.

Phase 6: in the BIOS

Once in the BIOS/UEFI, check:

• that the processor, total memory and drives are recognised;
• idle temperatures;
• enable the memory's XMP or EXPO profile;
• the boot order for installing the operating system from a USB stick.

If a newer BIOS version is available, updating it before installing the system is often a good idea.

Phase 7: final checks

After installing the operating system and drivers, run a short stability test: an hour of processor load, a memory test and a temperature check. Only then tidy the cables for good with ties and close the case.

In short

• Check compatibility before buying, not during the build.
• Fit CPU, RAM, SSD and cooler with the board outside the case.
• Check standoffs, I/O shield and every front-panel connector.
• On first boot, give memory training time to finish.
• Enable XMP/EXPO, check temperatures and stability, then close the case.