Computer Cases and The Different Types of Form Factors
The FormFactor is essentially a rough guide to the size of the case. There are no set dimensions, but each type normally fits within a range of measurements, and will house a specific size of motherboard. In this guide, we explain the differences between the form factors and some of their respective advantages.
Full-tower cases are the biggest cases available, with a height normally of 24” (60 cm) or more. The number of internal drive bays inside these cases can be between 6 and 10 so there is lots of room for expansion. They can have up to 11 PCI slots.
Mid Tower - ATX or Micro ATX Motherboards
The next case size down is the mid-tower case. These provide the sweet spot between upgradability and size. Mid-tower cases are the most widely used computer cases and are normally about 18” to 24” high (45cm to 60cm) and they usually contain 2 to 4 internal drive bays for hard drive additions, and a similar number of external bays (for CD/DVD drives and similar). These have up to 7 PCI slots.
Mini Tower - Micro ATX or Mini ATX motherboards
Mini-tower usually have 1 or sometimes 2 internal drive bays, to add extra hard drives. The mini cases normally stand at a height of 12” to 18” (30cm to 45cm). Expandability is a problem with these cases, as room can be limited. These have up to 3 PCI slots
Desktop - Micro ATX or Mini ATX motherboards
Desktop cases are simply tower cases turned on their side but are slightly slimmer so they could not fit a full-size graphics card (GPU) inside. They can hold a monitor on top of the case to free up space elsewhere. These have up to 4 PCI slots
Small Form Factor (SFF) - Micro ATX or Mini ATX motherboards
SFF cases are slightly smaller than Desktop cases but serve the same purpose of saving space. They are the same in thickness but are about 3/4 of the size. Most SSF cases have easy access to the inside with a pull handle on the side/top (depending on how you have it positioned) so you don’t have to mess about with any screws. These usually have up to 2 PCI slots.
Ultra-Small Form Factor (USFF) – Bespoke Motherboards
USFF cases are custom cases that are designed to minimize the spatial volume of a desktop computer. These computers usually take laptop size hard drives and memory. Most USFF computers use highly integrated motherboards containing many on-board peripherals, reducing the need for expansion cards so are often very difficult to upgrade. These smaller form factors, have more restricted air flow, so can get quite warm.
Micro – Bespoke Motherboards
Micro PC’s are the smallest there is. These PC’s are mainly used to attach to the back of monitors to save the most desk space. Like USFF PCs these also take laptop size hard drives and memory. Most can also have a Wi-Fi card fitted but this does vary so a USB Wi-Fi adapter is an option. Other upgrades such as expansion cards are very limited, and they do not have space for an optical drive.
More about Motherboards
A motherboard (also often known as a ‘Mobo’) is probably the most important part of your device. This is where every part of your PC/laptop connects to, such as:
The Motherboard’s Form Factor is a standardisation of dimensions and fit into three main types/sizes, from the largest to the smallest:
ATX – these are the biggest and allow for the largest number of expansion slots and ports, so are ideal for upgrading. They will only fit in the bigger cases.
Micro ATX – these are the most common type of motherboard size and are ideal for most users, including gamers. These are often put in full tower cases as well mid-sized cases because they are good value, and common.
Mini ATX – there are fewer slots than the larger Motherboards so adding more card is difficult but they still have the full functionality of larger boards.
Most motherboards have standard locations for power supply, location of mounting holes and the number/positioning of ports and slots for connecting components and peripherals, but they can differ across manufacturers.