It's difficult to envision the difference in size between the ITX and ATX form factors without first-hand experience, and a couple of measurements really don't convey the significance of the difference very well. So, we've put together a few illustrative photos to really give you a feel for the size of ITX. As you can see, once you lay them side-by-side, the difference between ITX and ATX is quite dramatic.
Many readers of this article will likely have never owned a computer of any size other than a full or mid-tower. You might be wondering what the big deal is, after all you've found space for a mid or full tower in the past, why bother going small now?
Admittedly many of the advantages are aesthetic but there are many practical perks as well, not the least of which is the smaller footprint. It's one thing to have a 16" (40.6cm) tall mid-tower or 21" (53.3cm) tall full tower, but it's another thing entirely to have a tiny 7" (17.7cm) tall mini-ITX box.
An ITX case is also designed to live on the desktop. If you have pets or toddlers, you might appreciate putting your case on a desktop where they are less likely to get at it. An ITX case has a very small footprint and they're also short, so it's much easier to find space for it on your desk. Many low-profile ITX cases can even mount to the back of LCD monitors where it will essentially have no footprint at all. Placing your computer case on a desk is also a good way to reduce the amount of dust it eats. With its small size, you could stuff an ITX case into or on top of a shelf or hutch, high above even the desk surface where it is much less likely to encounter dust and pet hair, as well as the wandering hands (and mouths) of children.
ITX is also a good option for less typical usage scenarios, like Home Theater PCs and network gatekeepers. The size and aesthetic design of many ITX cases work well with a home theater setup, where a typical tower isn't likely to fit. The small footprint makes it ideal for headless applications, where you won't need a monitor, like with dedicated firewalls. You can basically stuff the case into any odd corner and forget about it.
Another practical advantage of ITX is lower noise. While ITX machines aren't necessarily always quieter than towers, they tend to be because of their smaller size and fewer components. With less things under the hood pumping out heat, you don't need as much cooling, which means less fans and noise. In many ITX builds, the only fan in the whole machine is the one cooling the processor. Some ITX cases are even completely passive, with no fans at all, and the case itself acts like a large heatsink.
Another less obvious practical advantage is lower power consumption. Once again, this isn't a property inherent in ITX, but ITX machines generally use very little power simply because they have fewer components. Most ITX builds can get away with a power supply with less than 250W. Some don't have a conventional power supply at all, instead relying on a power adapter brick to supply the measly 100W it might need to operate.
What about the down side?
While there are many high points to using an ITX form factor in your next build, it isn't without its compromises. The primary problem also happens to be unavoidable, and that is the lack of expandability. There simply isn't much room for components so you are generally stuck with dual hard drives and a single expansion card. This means ITX simply will not work for some builds, like very-high capacity servers or AV recording and processing machines.
However, the lack of space for components should not be a deal breaker for many typical builds. Thanks to the relatively high quality of modern integrated components, most builds can easily get by with a single expansion slot. Limited hard drive space is also less of an issue with the recent mass availability of 1 terabyte drives at reasonable prices. Other traditional hurdles like relatively higher cost and low availability are starting to fade into the past as well.
In the next couple of pages we will show you some currently available products, a case and two motherboards, that go a long way to minimizing ITX's weaknesses and bringing the full-potential of its advantages to bear.