What Is A Computer Form Factor

As I began my hardware class in school I knew I was going to be learning some new stuff about a computer that I never really thought about besides the fact I use one. Hopefully what I talk about in this topic will help people get a better understanding of computer hardware, especially when might want to build one by scratch.

The form factor is used to determine what power supply, computer cases and motherboards you can use when building a fully customized computer instead of getting one pre-built; such as Dell, Apple, Sony, and Alienware. There are 6 form factors (including their variations that have been used since the 1980's; they include the AT (baby AT), ATX (Micro ATX, Mini-ATX, FlexATX), BTX, LPX (Mini LPX), NLX and Backplane.

Now to get a better understanding of each form factor the pictures here will show the standard types of computer cases that are currently being used, so once you read the information you will see a list that will tell which computer case can use the form factor properly.



Now that you seen the different computer cases it is time to explain each for factor, just a reminder that the form factors will be describe in this topic are based on motherboard specifications and not computer case specifications.

AT Form Factor



The AT (Advance Technology) Form Factor was first used by IBM in the 1980's, it's measurements are 12" x 13.8" and of course it is note that the AT form factor is no longer used since it has been replaced by the ATX form factor in 1995. Up until hte ATX form factor came out it was very difficult to install and of course upgrade, and reason why it was so difficult was that the CPU was set up in a way that it blocked the expansions slots. Thus making it even more difficult when trying to install cards into the computer; as you can tell by the picture you can see why it was so difficult.

But to fix this the Baby AT was design so it could be more flexible then it's predecessor, and the reason it was better and was the standard form factor from 1993-97 was it's size at 13" x 8.7". Also the baby AT had one more thing that made it better and that was it could fit into a ATX computer case, as the AT could not. Now in terms of air flow the baby AT power supply blew out the air instead of pulling in the air like the AT case did. However, the problem was not fixed with the position of the CPU and the drives, because this time the cables were stretched out to their limits in order to run a computer.

ATX Form Factor



The next form factor I will be talking about is the current standard form factor that is used by pretty much everyone to this day. The ATX (Advance Technology Extended) was introduced by Intel back in 1995 and what made this better then it's two predecessors was that it was a lot easier to install, maintain and even upgraded, it even help lower some of the costs to the hardware that was needed to install on a computer as well; which was a good thing when people started buying more and more PC's. Of course besides it size of 12" x 9.6", it solved motherboard arrangement in which the CPU no longer blocked the expansions slots. Of course some other factors came into play, such as the position of the power supply and the drives and of course the cables could be shorter as well, thus making them alot easier to connect and also to worry about static discharge when working inside the case. Then as time when on ATX produce the Mini-ATX which is 11.2" x 8.2" and the Flex ATX which is primarily used in the Slimline computer cases.

Then of course the Micro ATX which would be considered the second generation ATX due to the fact, it help lower costs ever more by reducing I/O slot on the motherboard and of course reducing the amount of power needed to run the computer as well. Of course the best part of the Micro ATX form factor is that can fit into any ATX casing such as the mid size tower.

BTX Form Factor



Up next is the BTX (Balanced Technology Extended) which was introduced in 2004-2005 to replace the aging ATX form factor, it was design so it could fit into a Full tower case into the small desktop casing (see pictures). It was designed so it could work with current technology such as Serial ATA, USB and PCI, and of course reduce heat with better airflow across the motherboard and the improvement of fans and other cooling systems (liquid cooling). However, due to the costs of converting ATX computers to BTX not many people took it like Intel thought it would. Intel would discontinue producing BTX hardware in 2006, however, like the other forms factors BTX will just need time for it to grow with that most smaller companies are still producing the BTX hardware needed if someone wants a BTX computer.

LPX Form Factor



The LPX (Low Profile eXtension) form factor was designed small computer, in which case only one expansion slot was used and of course that was used by a Riser card. Which was used to connect everything together in order to work, thus it was hard to maintain this form factor especially from the heat today's processors use. Same can be said about it's mini-LPX as well that it was hard to maintain against today's current technology.

NLX Form Factor



Basically the NLX (New Low Profile Extended) form factor was produced by Intel in 1998 to make up for the mistake of LPX form factor, it still uses the Riser card to connect everything together and of course the riser card was move towards the edge of the motherboard while the LPX was more in the center. However, another important upgrade was made and that was the NLX could use ATX power supplies while the LPX was restricted to LPX products, in this case made it more customizable in a sense you are not restricted to the type of power supply needed.

Backplane Form Factor



Now for the final form factor called the Backplane; this form factor in a sense is not a motherboard because of the fact it sites on the back of case instead on the side of one. The backplanes have two forms; the Active, which contains no circuits other the ones used for drivers, bus and buffer, and the other version called a Passive Backplane uses no circuits whatsoever, but in all actuality they are put onto the CPU card which is connected to a processor. You will find these form factors in all servers and rack mounted computer systems.

Now if you remember the pictures of the cases well here is a list of what form factor can be used in what.

Minitower - AXT, Micro ATX
Mid Tower - ATX, Mini-ATX, BTX, Micro ATX (depends on the ATX case type, in this case any Tower that is Branded with ATX 2.1, the micro can be used)
Full Tower - ATX, Mini-ATX, BTX,
Desktop - Although not as popular anymore because of their design they can be set up to use all form factors.
Slimline Desktop - NLX, LPX, Mini-LPX

So if you feel like building a computer from scratch like I am, this information is good know when purchasing all the hardware that is needed to build a computer.

This post has been edited by Saint_Michael: Jul 3 2007, 01:52 AM

Yeah BTX is an expensive form factor to build off of. I actually think I read some where that it is dead as you said, and form factors from companys like dell,hp,etc are called Proprietary(hope i spelled that right) they are custom built from the manufacturs leaving with limited upgrading capabilities. For example i have a really nice sony vaio that I got from my buddy he left it in his basement for two years and i ignored the fact that it had been in such conditions. So I just started it up and all the dust and possibly moisture from being in a basement left it useless when i heard a loud pop and display just went away and the system would not post after that. I started looking for a board to replace it with beacause i really like the case but had no luck because the motherboard is a proprietary form factor and uncompatiable with common form factors. Leaving me to have to order a replacement and get this that exact model was the only one to have the form factor that they designed.