Motherboard form factor

[Gene DeMambro]

Ok, a real simple question.

I do okay tinkering with my computer. I've added internal modems and sound cards and second parrallel ports to DOS, Win 3.1 and Win 95/98 systems. I just replaced my hard drive when my old one fried, and I replaced my system fan and power supply. So, I do okay.

The people at work even ask me to help with PC-related issues, before calling IS. I can almost always fix the problem.

So here's the question:

I read about motherboards. This form factor, and that form factor and all that. Are all motherboards, conforming to the same form factor, the exact same? For example, do all ATX form factor motherboards with an integrated sound card have the ports in EXACTLY to same place, so all I need to do is disconnect everything, remove to old board, add the new one and it fits in all the little holes for the ports and stuff? What about the internal connections for things like to power switch, the internal speaker, the HD in use LED and the reset button?

Thanx,
Gene

[This message has been edited by Gene DeMambro (edited October 23, 2001).]

[Arnie Elkins]

Short answer, it depends. Okay, so you wanted the long answer...

In theory, all motherboards of the same form factor should have all ports and connectors in the same places. In reality, it just isn't so. The ATX specification, for example, even includes a removable panel where the ports poke out of the case, so that you can insert the panel that fits your particular motherboard. This, of course, is in addition to the fact that there are 'baby' ATX boards, 'micro' ATX boards, etc. All the different flavors of ATX boards require different mounting holes in cases, and no two boards ever seem to use exactly the same mounting holes.

However, after saying that, I have yet to find a board that I could not mount in a particular case. They almost always require me to move a screw or two, but they always fit. There are, of course, nearly infinite combinations out there, and I have not tried quite all of them, so I am certain there are some combinations that will not work. And, of course, I would be remiss if I did not mention that there are always power issues to deal with. Old AT cases and boards were pretty simple. ATX brought new connectors for the motherboard, and new requirements for power supply manufacturers. AMD's Athlon processor brought new power requirements, even though they still were housed on ATX boards. And I don't even want to think about the requirements for the Pentium 4...new form factor, new power supplies, new memory...heck, you may as well chuck your old machine and buy a whole new one! Of course, that is what the hardware makers want you to do in the first place.

Sorry to run on, but this is not quite the simple question you may have thought you were asking. Shortest answer...is everything exactly the same? No. Most are, but there can be a lot of variation out there. However, reasonably modern cases/power supplies are made to deal with the variations inherent in motherboards. You may have to move a few screws and things, but normally you can upgrade a motherboard without changing the case.

Does that even begin to answer your question?

Arnie

[Allen M.]

All one needs to do is to go to pcsforeveryone.com, located right in Cambridge, check on the "parts and peripherals", and then click on one of the motherboard selections to the left to see the myriad of different types of motherboards that exist.

pcsforeveryone.com has excellent writeups for each of the four main categories of motherboards. Their writeups are not tailored to them, rather are standards pretty much across the board [pun].

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>and no two boards ever seem to use exactly the same mounting holes.
<HR></BLOCKQUOTE>Ain't that the truth, Arnie. However, standard cases and most, it not all, motherboards have extra holes and mounting studs so that there is always a fit.

This answer may help answer one of your questions, Gene:

I build a lot of PCs for myself, several a year sometimes, and first select the chip I want to use and then hunt for a motherboard to match it with the configuration of interest. My primary concern is the alignment of all the goodies with the back panel of the case, and although motherboards may vary in size, hole count and position, this panel alignment is critical; it either mates or not.

ALL the motherboards AND cases I have purchased over the past number of years fit each other without a hitch. One case I still use is over 5 or 6 years old. Motherboard manufacturers have gone great lengths to insure a fit in the cases, old or new.

Internal connections are usually always compatible with the PCs I have built.

With the new AMD, over 1-GHz, chips a heftier power supply is required. They seem to be universal both in hardware mounting and connector attachment. I use 350 watts, but 300 will do.

HOWEVER, manufacturers often use their own custom power supplies, custom boards, and custom cases which break all the rules for compatibility, both mechanical and electrical.

Remember that older boards are super slow, Gene, not just because of the processor speed, but also because of the board bus speed.

Sure has become a jungle out there, hasn't it Arnie?


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Allen Moulton from Uechi-ryu Etcetera