My atx psu on this 486 board is fine. No -5v but nothing I have needs it. Board runs solidly.

Used to use the psu in a core2quad with 2 'proper' hard disks and a dvdrw. Dont think it feels stressed now.

Agree everything will fail eventually, including me! Wouldn't worry too much - if you like the AT caae style and can absorb the cost, go for it. Want something cheaper and dont have that much space - an mATX is fine for baby-at if you don't mind losing a few slots. If you do, I'd imagine you could use an ATX case (but I haven't actually done it 😀)

The I/O issues with AT systems will make you appreciate what an improvement ATX was/is. Back in the early 2000s, I bought a used Chaintech 5AGM2 in order to build a low cost computer for my aunt who didn't have one, since it allowed me to use an AT case I already had. But on that board, the USB header used very tiny pins, and standard USB dongles will not fit. I found a dead CDROM that had a couple of five pin connectors that were close to the correct size, and I was able to shave them down to make them fit, then solder them to a standard USB dongle - it was quite a bit of extra work. And you run into many similar issues with serial port cables having different pin outs, PS/2 mouse dongles, etc. It likely wasn't as much of an issue when you bought this hardware new, since the correct cables were included, but they so often seem to get lost when you're buying them used.

The biggest problem with AT cases is finding one in good condition that can fit on your desk without hitting the ceiling.

I was browsing for them earlier. I have 3 annoyingly cramped Baby AT cases and thought there must be something of reasonable size, similar to ATX. Nope, apparently it was cool back then to make your computer stupidly tall.
It's not to fit big motherboards either. The motherboard trays (when shown) look normal to me. The PSU is above that, and then they add a few feet of air.
I guess the idea was to support maybe two full height hard drives and dual 5.25" floppies and... I don't know what else. But it just looks very impractical now.

Right, I also never understood the purpose of full tower AT cases, although I remember thinking at the time they would surely be used for housing some sort of super powerful computers because bigger = better. The only advantage I can see now is the increased number of external 5,25" drive bays, although I don't know who would need 4 CD-ROM drives and 2 5,25" floppy drives in 1994.

One important thing:
Don't turn on anything before you inspect it carefully first.
Just last week I got an AT desktop case with an incorrectly wired PSU switch and it tripped the circuit breaker when I turned it on.
Always check the 110/220 switch on the PSU.
The power connector thing is easy, the black wires always go together. The problem starts with proprietary PSUs where you often have the same AT style connector and a completely different pinout.
My AT desktop cases are all good quality, no sharp edges. You can take it apart completely so cleaning is easy. The front bezel is usually held by screws and the plastic parts often break or let go.
I hate the plastic standoffs that are everywhere in AT cases. They are hard to remove and hard to install, break all the time and don't properly hold the board in place. Replace them with metal standoffs with screws if you can.
Also rumors about the weight are true, my last desktop case was 17 kg (37 lbs) assembled as a 286 system.

devius wrote on 2020-08-10, 10:24:

Right, I also never understood the purpose of full tower AT cases, although I remember thinking at the time they would surely be used for housing some sort of super powerful computers because bigger = better. The only advantage I can see now is the increased number of external 5,25" drive bays, although I don't know who would need 4 CD-ROM drives and 2 5,25" floppy drives in 1994.

Tape drives, multiple HDDs, etc could easily eat up a full tower case. Especially considering that some SCSI hard drives of the era were full height.