AT Case and Power Supply for ATX Motherboard?

salsal

Member
Aug 3, 2001
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I have an old pentium 166 MMX computer sitting around somewhere and I want to upgrade the whole thing. It has an AT case and power supply. Can I stick an ATX or m-ATX motherboard in it? Anything else do I need to do to make it work?
 
Aug 23, 2000
15,509
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most likely you'll have to get another case. The ATX design has wires that go from the power button to the motherboard, AT the power button is wiered directly to the PSU. So unless you have a case/psu that can go eitherway, your SOL.

Besides, if you're gonna buy a psu the cases that come with it will only be like $10-$15 more for a generic.
 

dszd0g

Golden Member
Jun 14, 2000
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With the exception of some ATX style-AT cases that were made during the transition, AT cases are completely incompatible. The AT case uses an AT keyboard plug (large circular), not the PS/2 used in ATX. ATX cases have a plate where the motherboard sticks all its connections out the back, while AT cases are missing the plate and instead have some serial and parallel port covers that can be bent out.

While if one looks really hard, one can find AT motherboards for newer processors: they are not mainstream. You will be much better off building a new computer from scratch than trying to use anything out of that machine. The possible exception of any modern PCI cards it might have. The Pentium 166 is a later modem Pentium and should have mostly PCI slots, the earlier Pentium 60, 75, and 90 systems generally had more ISA and/or VLB slots (along with a couple PCI slots) which would be of no use to you now.
 

GregMal

Golden Member
Oct 14, 1999
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Take a close look at your case. I have one of those AT/ATX cases.
All I did was replace the PS and purchase an ATX switch.
Works fine for me..........
Greg
 

Buk

Senior member
Oct 9, 1999
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Your biggest problem will be the area of the ps/2 keyboard/mouse sockets, serial ports, etc at the rear of the case. ATX cases have a shield that fits these connections closely to prevent emi from leaking out of the case and causing interference with other electronic devices nearby. You might could dremel out the area to fit the atx mobo and have no problems. The power switch is just a normally open momentary switch. You could pick up one at radio shack and 'stealth' it by mounting it in the rear of the case. Just connect it with leads long enough to get to the header on the mobo. Of course, then you would have to think of something creative to hide the now no-longer-functioning push button switch on the front of the case (or you could leave it and let your friends try - unsuccessfully - to boot up your comp).