Lesson 9- Case and Power Supply – custom computer case


In lesson 9 we’ll cover the computer case along with the power supply, what features and specs to look for when shopping for a custom computer case, and how much you can expect to pay.

The computers case holds all of the internal components and provides power through its power supply. Computer cases come in two basic form factors or shapes. These are atx tower, micro atx.

Form Factors

ATX Tower cases are the most popular. They allow for the greatest expansion, they’re impressive to look at and are ideal for most home computer systems. Within the ATX tower form factor there are two sizes, Midsized and Full.

Midsized towers typically have 3 or 5, 5.25 inch drive bays for adding CD/DVD drives and 3 or 6 slots for 3.5 inch hard drives.

Full size towers have between 5 and 12, 5.25 drive bays and 4 to 10, 3.5 inch slots.

Some cases will also have 2.5” bays for solid state drives.

Deciding which size tower to choose, comes down to how many hard drives and DVD or blu-ray drives you intend to have in your computer.

Mid or full tower atx cases support the ATX motherboard standard.  ATX is the standard size motherboard used in most computers today.

Extended ATX (E-ATX) and Extra Large ATX (XL ATX) are larger versions of ATX used by higher end motherboards that need the extra space for more features. If you choose an Extended or XL ATX motherboard make sure you also get a Extended or XL ATX case.

Micro ATX is a smaller version of the ATX motherboard, made for smaller Micro ATX cases.  You can also put a Micro ATX motherboard into a regular ATX case if you like.

You can find Micro ATX cube, desktop, slim and towers cases.

Micro ATX cases are very popular for space savings and portability with 1 to 3, 5.25 inch bays and 1 to 4, 3.5 inch bays


The quality of the case is important. It should be solid, have no sharp edges inside and should be easy to work with. Look for a case that is easy to move parts around in. When you remove the side of the case it should be generally open, with easy access to the motherboard area, and drive bays.

Power Supply

The power supply takes the electricity from the wall outlet and converts it to power all of the components in your computer.  For both ATX and MicroATX power supplies, the current standard is called ATX12V 2.3 or EPS12V 2.91.  The specification is the same, but Micro ATX power supplies are smaller in size.

Most ATX cases do not come with a power supply, while most Micro ATX cases do come with a power supply.

It’s important that the power supply you choose provides enough power to support all of the components in your system. A 400 watt power supply is a minimum. If you plan to add several hard drives and CD, DVD, or blu-ray drives you should look for a 500 to 550 watt power supply.

To figure out how many watts your computer will need do a Google search for power supply calculator.  You’ll find the extreme power supply calculator.  Enter all of your hardware into the drop downs, click Calculate and it will tell you the wattage requirements.  Add an additional 100w to be safe.

SLI and Crossfire Requirements

The latest video cards can also pull a lot of power. Check the video cards specs for power recommendations especially if you’re going to be using 2 or more video cards in SLI or Crossfire mode. Also PCI Express video cards require a special power connector so check the power supply for PCI Express/SLI or Crossfire support. You can also add this connector to a standard 4 pin connector with a PCI Express power adapter.

Modular Cables

On most power supplies, all of the cables are attached and can’t be removed even if you don’t need to use them in your computer. This means you have to tuck away the unused cables in the case which takes up room and can cut down on the airflow which will effect the cooling of the components in the case.

A power supply with modular cables lets you only plug in the cables you actually need. You can store the extra power cables for future use.

To go along with the power supply be sure to buy a power strip with surge protection. This will provide power to the computer, monitor, speakers and other external components.
Uninteruptable Power Supply (UPS)

To go along with the power supply be sure to buy a power strip with surge protection. This will provide power to the computer, monitor, speakers and other external components.

You might consider buying an uninteruptable power supply or UPS which replaces the standard surge protector.  A UPS is a battery backup that provides continues clean power to your PC and other devices.  If the power goes out for an extended period, usually 10 to 15 minutes, the UPS will save your documents, close the applications and shut down the computer gracefully.  Prices range from 80 to 200 dollars, depending on your computers power requirements, in watts and how long you want the battery to last, if your electricity fails.

What to look for when you Buy

When you purchase a tower or desktop case

  • Make sure it comes with, or buy separately, an ATX12V 2.3 or EPS12V 2.91 power supply with at least 400 watts of power.
  • Don’t be afraid to pay extra for good cooling options, quality construction and ease of use. You’ll thank your self later.
  • If you’re planning on using SLI or Crossfire, look for support in the power supply.
  • $40 for a case with a power supply is a good minimum amount. Paying more will get you a better case and power supply, but don’t pay more that $200 unless it’s the case to beat all cases.

In the installation lessons we’ll go over how to install all of the internal components into the case and connect the cables to power them.

Case and Power Supply Warranties

Computer cases are generally very reliable and will last for many years. That said, the fan in the power supply can wear out over time.

Most case and power supply manufacturers offer a 1 year warranty, though you can find cases and power supplies with 3 years of coverage.

Case and Power Supply Reviews

To find more reviews do a search in your favorite search engine (Google, Yahoo) for the model number of the case or power supply you’re interested in.

Buying a Case and Power Supply
Whether you buy a case with power supply, or the power supply separately, there is no shortage of custom computer case choices. Below are several sites that will help you find the lowest price from a reputable merchant.