Case Size and Form Factor

PC cases come in many different shapes and sizes, and it is essential to decide up front the size of your new PC as this will greatly affect your choice of parts.

Form Factor

There is a standardized system for ensuring compatibility in regards to the physical size of some PC components, called the form factor. The form factor affects both the motherboard and case and the two must be compatible. The most common form factors you will find today are ATX (the “standard” size), Micro-ATX, and Mini-ITX. There also exists Extended ATX (also known as EATX) which is larger than ATX, and Nano-ITX and Pico-ITX which are incredibly small, smaller than Mini-ITX. Other form factors exist, but are incredibly uncommon.

Power Supplies also have a form factor, and the most common ones are ATX PS/2 (the “standard” size), ATX PS/3 (sometimes referred to as “Micro-ATX”), SFX (also sometimes referred to as “Micro-ATX”), Flex ATX (Sometimes referred to as “Mini-ITX”), and TFX.

If you just want to build a standard PC, you will want to look for an ATX case, motherboard and power supply. However, if you find a better deal on a smaller motherboard or power supply that fit your needs, don’t shy away, just double check that they are compatible with your chosen case.

If you want to build a small form factor PC (called a SFFPC) you will be looking at Micro-ATX and Mini-ITX. Similar to above, you might find a Micro-ATX case that also supports the smaller Mini-ITX motherboard, or a smaller format of power supply, be sure to check the case specifications to determine which formats are supported.

Low Profile / Slim Cases

Low profile or slim cases will have half-height expansion slots, which is what allows them to physically be so slim. The important consideration here is that if your case has half-height expansion slots, then by necessity, all of your expansion cards must also use a half-height bracket or “slim” design. This will severely limit your choice of components and also tends to increase their cost.

Graphics Card Size

One special consideration when selecting a case is the physical dimensions of your graphics card. In recent years, GPUs have ballooned in size and even though a graphics card may appear compatible with your case at first glance, it might not actually fit in reality.

First, if you plan to use a low profile or slim case, you will probably need a low-profile graphics card which has a half-height bracket design and is generally slimmer in width and shorter in length than a standard GPU. Note that many low-profile GPUs can have their bracket swapped out for a full-height bracket and can be a good option for a small form-factor case that has full-height expansion slots.

Next you should consider the width. This is usually measured as “slot width”, which refers to the number of expansion slots that the card occupies. You will see values such as single, dual, 2.2, 2.3, 2.5, 2.75, triple and even quadruple slot width. It’s quite simple, if the slot width is single, it will fit in the space of a single expansion slot. Dual will take up two expansion slots, and will usually also have a double bracket meaning that it physically slots into both expansion slots on the back of the case, and a fractional width, 2.5 for example, will fill the physical space inside the case of two and a half slots.

Final consideration is the length of the graphics card. This can vary wildly, from a tiny 69mm up to a whopping 394mm! Consult the case specifications to know the maximum length of expansion cards.

Integrated or Dedicated Graphics

An integrated graphics card is one that is built into another component, usually either the processor or motherboard, and removes the need to buy a separate, dedicated card. A dedicated graphics card is one that is a component all in it’s own, that plugs into one of the motherboard expansion slots, usually a PCIe x16.

The advantages of integrated graphics are decreased overall build cost and lower power consumption, however, an integrated GPU will only provide basic graphics, and should only be considered for a PC that will be limited to basic tasks like word processing and web browsing, or entry-level gaming.

If you plan to run visually demanding video games, or do video editing or other 3D rendering, then you will almost certainly need a dedicated card. Note that even if you buy a dedicated GPU, a processor with integrated graphics will not hamper your performance in any way, as the integrated GPU it will automatically disable itself upon detection of the dedicated card.

If you have a limited budget, you could buy a processor with integrated graphics to use for now and upgrade to a dedicated GPU later on when more money is available.

Dedicated Graphics: SLI and CrossFire

If you are buying a dedicated graphics card, there is an additional feature to consider: multiple GPUs. Nvidia calls it SLI and AMD calls it CrossFire, and the idea is that you can connect two or more graphics card together in parallel to achieved greater graphics processing power.

Usually it is more expensive to buy two of a mid-range graphics card than it is to buy one of a high-end card, so when putting together a new build you wont usually have multiple cards right away. But in the future when you are upgrading this PC, if your existing graphics card is SLI or CrossFire compatible, it will almost certainly be less expensive to buy a second older graphics card and run it in parallel than it will to buy a new high-end card. With this in mind, you may want to look for a graphics card that is SLI or CrossFire compatible, to keep your upgrade options open down the road.

Integrated or Dedicated Audio

Integrated audio is when the motherboard has an audio chipset built in. This means you can plug speakers directly into the motherboard. Nearly every motherboard on the market today has integrated audio.

For the vast majority of users, integrated audio will suffice, and there is no reason to buy a dedicated sound card. Some use cases where you might consider a dedicated card include recording or mixing audio, studio use, high-end home theater setups, or you are an audiophile and want a higher fidelity audio output than on board audio can provide.

Solid State or Hard Drive

Solid State Drives or SSDs are significantly faster than Hard Drives but also more expensive. The good news is that in recent years the prices have dropped a lot and at this point there is no reason that you should not have at least one SSD in your PC.

Most builders buy one SSD on which they will install their operating system and most of their applications, then pair it with a Hard Drive where they keep personal or work data, movies, music, and video game installs that are too large to fit on the SSD. If you can afford to do so, you may opt to just buy one large SSD, but this is not necessary. Inversely, if your budget is tight, you can just buy one large Hard Drive – on a low end machine the performance impact will be minimal anyway.

CD, DVD or Blu-ray

CD, DVD and Blu-Ray drives, also known as Optical Drives, are optional and whether or not you have one comes down to preference. Having at least one optical drive will make installing an operating system easier, but there are other ways to accomplish this.

Many builders opt for an inexpensive CD/DVD combo drive which will allow installing software from CD or DVD, listening to music CDs, and watching DVD movies. The only reason to buy an expensive Blu-ray drive would be if you want to watch Blu-ray movies.

A CD-RW or DVD-RW drive would allow you to burn CDs or DVDs respectively, but these have fallen out of favour due to the availability of inexpensive large-capacity USB drives. However if you want to burn music to CDs or home movies to DVDs, this might still be a consideration.