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How to add an expansion card to your desktop computer

Updated June 26, 2024

Have you ever wanted to add more USB ports to your desktop computer? Or a graphic card or wireless (Wi-Fi) network adapter? Here's how to add an expansion card to your desktop computer.

How to add an expansion card to your desktop computer

One of the most incredible things about desktop computers is that you can add more functionality to them by installing an expansion card. Expansion cards range from graphic cards and RAID controllers to USB ports and wireless (Wi-Fi) network adapters. But before you can do anything, you will need to know a few things:

  • What expansion slots do you have available on your computer?
  • What is the height (full or half) of your computer case?
  • What are the power requirements for the expansion card you want to install?

But before you can do anything, you need to know what expansion card slots your desktop computer may have available. The PCI Express (Peripheral Component Interconnect Express (PCIe, PCI-e)) bus type is the most common expansion slot. See #1 and #2 in the installation instructions at the bottom of this article to find out how to open up your computer case to check.

The different PCI-e bus types

Now PCI-e slots and expansion cards come in different bus sizes, varying the number of connectors and bus speed. Generally, the more connectors, the faster the transfer rate.

A photo of a PCI Express x16 slot
PCI Express x16 slot (82 connectors per side x 2 sides = 164 connectors)

A photo of a PCI Express x4 slot
PCI Express x4 slot (32 connectors per side x 2 sides = 64 connectors)

A photo of a PCI Express x1 slot
PCI Express x1 slot (18 connectors per side x 2 sides = 36 connectors)

The two different computer case heights

Once you know what expansion slot(s) your desktop computer has available, you need to find out what height (full-size or half-size) your computer case is.

A photo of a full-height expansion slot
Full-height expansion slot

A photo of a half-height expansion slot
Half-height expansion slot

Now, a full-size case can use either full-size or half-size expansion cards. If the expansion card you are looking at installing is low profile, the manufacturer usually includes full-size and half-size mounting brackets. If the expansion card is full height, you will not be able to put it in a half-size case, so double-check it before purchasing.

Check the expansion card power requirements

Now, everything you plug into your motherboard requires power, including the drives, processor(s), and memory modules. Check the specifications for the expansion card you want to install and determine how much power it requires.

Next, you need to check how many watts your power supply delivers. The power output is crucial. Typically, there is a power output table on the side of the power supply inside your desktop computer that tells you the maximum DC output.

A photo of a typical desktop power supply output table
A typical desktop power supply output table

If your computer is a low-profile or Small-Form Factor (SFF), knowing its power output is critical. Most SFF computers have smaller power supplies (physical size) with lower power output. Generally, the output of an SFF power supply is less than 300 watts, which may or may not have enough power to run an additional expansion card.

To top it off, the expansion card you want to install might even require more power than the PCI-e bus can provide, thus requiring an additional connection or two from the power supply.

High-end graphic cards are known to require an additional PCI-e power plug(s) from the power supply. If your power supply doesn't have enough PCI-e (6 or 8 pins), Molex (4 pins), or SATA (15 pins) connections, you will need to upgrade it.

A photo of a video card that has both 8-pin and 6-pin PCI-e power connections
A video card that has both 8-pin and 6-pin PCI-e power connections

Now that you have the required information and purchased your expansion card, it is time to install it.

Installing an expansion card in a desktop computer

Installing an expansion card is relatively easy. You may or may not require tools, as some computer cases are tool-free. Most of the time, you need a Philips head screwdriver to open the side of the case and secure the expansion card to the computer case.

  1. Disconnect the power cord from the computer. After disconnecting the power cord, place your hand on any metal part of the case to discharge any residual energy. Never work on a system that is plugged in and energized.
  2. Open the computer case. This step usually requires removing the side or top panel. Look at the back of the computer case and determine which side the motherboard connections are on. The side panel you need to remove is on the opposite side of these.
  3. Remove the expansion slot cover panel on the backside of the case. Some expansion slot panels have a screw holding them in place; some are stamped right into the metal back of the case. If it is a stamped panel, you will have to work it back and forth to break it off, so be careful not to cut your fingers.
  4. Install the expansion card. Most cards will slip right in, but make sure the notched edge of the mounting bracket slides down into the slot in the case. Sometimes you have to give it a little push from outside the case to get it in. Once it is in place, secure it down.
  5. Replace the side of the case, connect the power cord, and power your computer up.

If Windows doesn't automatically install the driver for the expansion card, you may have to use the installation disk that came with it. If the expansion card did not come with installation media, go to the manufacturer's website and download it.

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