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Building a Baby-AT system in an ATX case.


Veteran Member
Sep 30, 2011
Fairfield, CA, USA
One thing I've found is AT cases are darn near extinct locally, but ATX cases are everywhere. After some playing around I found that my Baby AT motherboard just about had every mounting hole line up with that of a spare ATX case I had laying around. While building I documented most steps to show just how easy it is to do.

The first thing I did was grab the case. You may notice here that there are no standoffs for a motherboard, the previous owner kept those for some reason, so I had to go find my own, which came in handy as I can choose the holes I need them in.

The next thing I did was make sure the motherboard lined up properly, even without standoffs I was able to do this.

After that I marked off the holes where I would need the standoffs, that way I don't have any below the board that can possibly short something that shouldn't be.

I then went ahead and put in the standoffs, and tested once again to make sure it was correct.

One thing you might notice is the top left and right have no support as there are no places up there to put a standoff, that's where one of those stupid plastic things from an old cheap case come on.

Once I had it entirely screwed in place, it was fairly secure, with a bit of a loose spot below the ram slots, but that's a specific case design flaw and not so much a motherboard flaw. That GeForce FX5200 is there once again to make sure my expansion slots lined up properly as having a PC with no means of video or anything is kinda pointless.

Now, we know that's all working, but we do need a power supply. This is where I'm going to say don't use an Antec 300, use something with a top mounted power supply otherwise your motherboard power cables are going to be a bit of a pain. If you do use a bottom mounted PSU case, try using an ATX to AT power supply adapter as ATX power supplies typically have longer cables, and if not it's not too terribly hard to find an extension for an ATX power supply.

Now, there is one thing that I still don't have done and that's a power switch. A power switch is the hard part, but my plan is to sacrifice a 5.25" bay faceplate to put a hole in to mount the power switch, but that I didn't get done today.

And finally, some things I learned from this.
1.) Top-mounted power supply would've been far easier to put in place.
2.) Use a case with a 3.5" drive bay, the Antec 300 doesn't have one.
3.) Don't use a case with a hole to mount CPU cooling brackets for an ATX motherboard.

Other than those, this here worked out quite well, with plenty of left over room inside the case for whatever. This also provides me with a couple 120mm fan mounts for better airflow than a standard Baby AT case, and a bit quieter fans at that.