Connect the 24-pin motherboard power connector first

Start by plugging the large 24-pin (or 20-pin on older boards) power connector into the motherboard. This is the main power delivery line and should go in before anything else. The connector is keyed so it only fits one way, and you'll feel it click into place when seated properly.

The reason to do this first is practical: the motherboard is the central hub that everything else connects to, so powering it establishes your foundation. If something goes wrong during the rest of the build, you'll know the primary power path is solid. It also keeps your hands and workspace organized — you're working from the largest, most obvious connector down to the smaller ones.

Key Takeaways

  • The 24-pin motherboard connector goes in first because it's the main power line and the central point everything else branches from.
  • The 8-pin CPU power connector (usually near the top of the board) should go in second, before you install the CPU cooler.
  • GPU power connectors (6-pin, 8-pin, or both) come next if your graphics card needs them, but only after the card is seated in its slot.
  • SATA power and fan connectors are last because they're optional depending on your specific components and can be routed after everything else is in place.
  • Working in this order keeps your workspace organized and makes it easier to troubleshoot if the system doesn't power on.

The 8-pin CPU power connector comes second

After the 24-pin motherboard connector is seated, locate the 8-pin (or sometimes 4-pin on older or lower-power boards) CPU power connector. This is almost always positioned near the top of the motherboard, close to where the CPU socket is. Plug it in before you install your CPU cooler, because the cooler will sit directly over or very close to this connector and make it harder to reach afterward.

Some motherboards have a second 4-pin connector nearby for additional CPU power stability. If yours does, connect that too at this stage. These connectors are smaller and easier to miss, so double-check your motherboard manual if you're unsure whether your board has one.

GPU power connectors come third (if your card needs them)

If your graphics card requires external power — most modern cards do — install the card in its PCIe slot first, then connect its power cables. Most cards use a 6-pin connector, an 8-pin connector, or both. Some high-end cards may have two 8-pin connectors. Check your card's manual or the connector labels on the card itself to see what it needs.

The reason to do this after the motherboard and CPU power is that the GPU is a secondary component. The system can boot without it (using integrated graphics if your CPU has them), but it cannot boot without motherboard and CPU power. Connecting the GPU power after those two are solid means you're building outward from the core system.

SATA power and fan connectors come last

Once the main power lines are in place, connect SATA power cables to any storage drives (SSDs with SATA connectors or mechanical hard drives). These connectors are keyed and only fit one way. If your power supply has modular cables, you may not need to connect SATA power at all if you're using only NVMe SSDs, which draw power directly from the motherboard.

Fan connectors on the power supply (if your supply has them) also go in at this stage. Most modern power supplies don't have separate fan connectors — the fan runs based on internal temperature sensing — but if yours does, it's a low-priority connection. Case fans and CPU cooler fans typically connect to the motherboard's fan headers, not the power supply, so this step may not apply to you at all.

Check your motherboard manual for your specific board layout

Every motherboard is slightly different in where connectors are positioned and what optional connectors it includes. Before you start connecting power, spend two minutes looking at your motherboard manual (the physical one in the box, or a PDF from the manufacturer's website). The manual will show you exactly where each connector goes and whether your board has optional connectors like a second CPU power pin or a 12V rail connector.

Knowing this ahead of time prevents you from connecting something in the wrong spot or missing a connector entirely. It also tells you which connectors are truly required versus which are optional for your specific setup. Some boards have connectors that only matter if you're overclocking or running very high-end components.

What to do if a connector won't fit

Power connectors are keyed, meaning they have a notch or tab that prevents them from going in backward or upside down. If a connector won't fit, do not force it. Stop and check the orientation. Forcing a connector can damage the pins on the motherboard or the connector itself, and that damage is often not repairable.

If it still won't fit after checking the orientation, verify you have the right connector. A 24-pin connector looks different from an 8-pin, and a 6-pin GPU power looks different from a SATA power connector. If you're genuinely stuck, take a photo of the connector and the motherboard port and compare them side by side. The manual's diagram will also show you what each port should look like.

Frequently Asked Questions

Do I have to connect power in this exact order?

No, but this order is logical because it works from the largest, most important connectors down to smaller ones. As long as everything is connected before you power on the system, the order during assembly doesn't matter. The order matters for troubleshooting: if the system won't start, you know the main power lines were connected first and are more likely to be correct.

What if my power supply has modular cables and I'm not sure which ones to use?

Start with the cables labeled for motherboard power and CPU power — these are non-negotiable. Then add GPU power if your card needs it. SATA and fan cables are optional depending on what storage and cooling you have. Your power supply manual will show which cables go where, and the connectors are keyed so they only fit in the right ports on the supply.

Can I connect power cables while the power supply is switched on?

No. Always switch off the power supply and unplug it from the wall before connecting or disconnecting any cables. Connecting power cables to a live supply can damage components or cause injury. Once everything is connected and you're ready to test, then you switch the supply on.

My motherboard won't power on. Did I connect something wrong?

Check that both the 24-pin motherboard connector and the 8-pin CPU power connector are fully seated — they should click into place and sit flush. Reseat them by pulling them out slightly and pushing them back in firmly. Also verify the power supply itself is switched on (there's usually a switch on the back). If it still won't power on after checking these, the issue may be elsewhere, like the power button connector or a component failure.

Do I need to connect the optional 4-pin CPU power connector if my board has one?

Check your motherboard manual. Most boards list it as optional for standard use and required only for overclocking or very high-end CPUs. If you're building a standard system with a mid-range CPU, you can usually skip it. If you're unsure, connecting it doesn't hurt and provides extra stability, so it's a safe choice.