I don't think I've personally seen any in the "modern" AT format, but I think I came across a couple of 5170 size /server/fulltower type AT supplies that were passive years back, so watch out you don't accidentally order one of those, because that's the OG AT. Then there's been a few non-standard shaped ones that various OEM had made custom for their systems, but both of the ones I own like that are very low wattage, like 65W and 110W. Also, the design of case these were in, though technically the PSU was passive, the case was mostly closed apart from a fan on the other side and most of the air passed out through the back grille of the PSU. So passive-ish.

Thanks. You bring up a good point about air flow. I'm not sure many custom build AT cases had much in the way of ventilation.

I made one by, you bet, removing the fan from one that had it (as part of an electronics swap) 😀

Result wasn't bad according to my finger vs the heatsinks (unplug first!!!), certainly better than the AMD 286@12 at which the only (system) fan was loosely aimed by the designer, though this was a "modern", integrated graphics and I/O 286 system...

A few months ago I found some parts in the garage and assembled an ATX P2 Celeron 433 system, also fanless because when we replaced the fuse back in 2007 or something (yes it ran then-fully-updated XP) we forgot to reconnect the huge and relatively quiet fan inside, it held at least 20 minutes but then it started smelling of hot dust like most TVs, so I had to stick a fan outside it until the next day (after spending the night unplugged) to reconnect the internal one 😜

Ryccardo wrote on 2023-11-05, 21:09:

I made one by, you bet, removing the fan from one that had it (as part of an electronics swap) 😀

Result wasn't bad according to my finger vs the heatsinks (unplug first!!!), certainly better than the AMD 286@12 at which the only (system) fan was loosely aimed by the designer, though this was a "modern", integrated graphics and I/O 286 system...

A few months ago I found some parts in the garage and assembled an ATX P2 Celeron 433 system, also fanless because when we replaced the fuse back in 2007 or something (yes it ran then-fully-updated XP) we forgot to reconnect the huge and relatively quiet fan inside, it held at least 20 minutes but then it started smelling of hot dust like most TVs, so I had to stick a fan outside it until the next day (after spending the night unplugged) to reconnect the internal one 😜

Yah there were later AT supplies with a temperature controlled fan that basically didn't cut on until you really flogged the system hard in hot weather, so derating a higher powered one by 100W for passive output is probably do-able... if you are going to keep a very good eye on it. .. or finger as the case may be... though there's main wall voltage running around loose in there so finger real careful too.

Ryccardo, interesting idea. It sounds like a bit more trouble though. 😀

Depends on the design of the power supply. Older style AT power supplies often used one or more ceramic power resistors to operate correctly. Without airflow those could reach 100+ degrees (Celsius). More modern designed AT power supplies didn't rely on those and ran pretty cool at moderate wattages. As far as the PC itself needing an exhaust fan via the power supply fan...well PCs didn't really need any airflow at all until about the DX2-66 era.

kingcake wrote on 2023-11-06, 03:42:

Depends on the design of the power supply. Older style AT power supplies often used one or more ceramic power resistors to operate correctly. Without airflow those could reach 100+ degrees (Celsius). More modern designed AT power supplies didn't rely on those and ran pretty cool at moderate wattages. As far as the PC itself needing an exhaust fan via the power supply fan...well PCs didn't really need any airflow at all until about the DX2-66 era.

Do you think a 486 running 100+ Mhz (with a CPU fan) would require a PSU with a fan to help move air?

thisIsLoneWolf wrote on 2023-11-06, 05:30:

kingcake wrote on 2023-11-06, 03:42:

Depends on the design of the power supply. Older style AT power supplies often used one or more ceramic power resistors to operate correctly. Without airflow those could reach 100+ degrees (Celsius). More modern designed AT power supplies didn't rely on those and ran pretty cool at moderate wattages. As far as the PC itself needing an exhaust fan via the power supply fan...well PCs didn't really need any airflow at all until about the DX2-66 era.

Do you think a 486 running 100+ Mhz (with a CPU fan) would require a PSU with a fan to help move air?

Yeah at that point I would feel more comfortable with some kind of airflow in the case itself. But you could buy a real cheap thermocouple, run the wire into the case and see if the heat really builds up over time or not.

Thanks for all your advice.

Alternative solution is getting silent ATX PSU and AT PSU adaptor cable.

Bruno128 wrote on 2023-11-06, 19:05:

Alternative solution is getting silent ATX PSU and AT PSU adaptor cable.

This seems like a good option.

thisIsLoneWolf wrote on 2023-11-06, 23:35:

Bruno128 wrote on 2023-11-06, 19:05:

Alternative solution is getting silent ATX PSU and AT PSU adaptor cable.

This seems like a good option.

PicoPSU might also work, depending on power requirements.

An original PicoPSU (not the Chinese knock-offs) is quite capable. I use it to power a 386 SX, a Pentium MMX 233, and a Pentium 4! All machines have two floppy drives, CF cards as HDDs, dedicated sound cards, VGA cards (plus a CD drive on the Pentiums). Though I haven't tried a Voodoo or a similar strong 3D accelerator... but yeah. I vouch for those amazing things. They do get a little hot, so I still recommend a quite fan to circulate air across the case.