Sidney

Silent power supplies for PCs are, basically, a big gyp.

PCs are, you see, meant to be cooled by air flowing through them. Plain free convection doesn't cut it; you need at least one fan for any normal PC.

A lot of PC parts are happy running at surprisingly high temperatures - just because you can't hold your finger on your hard drive doesn't mean it's destined for an early grave - but if there's no ventilation at all, any normal PC will get really hot, and then proceed directly to the scene of the crash.

Fans make noise. So, obviously, a truly silent computer has to have (among other things) a silent power supply, with no fan.

Good luck making such a system work, though, unless you opt for weedy Eden boards and laptop drives. Yes, careful design and component choice has produced some decent fanless computers over the years, but modern PC components make it very, very hard.

The most straightforward way to achieve the fanless feat with normal components is by using Zalman's giant fanless cases, which're definitely an engineering landmark. But just the case by itself costs as much as a whole low noise P4 system, plus half the price of an OK monitor.

Water cooling doesn't solve the problem, because you need a radiator, and the radiator needs a fan. You could use an irrationally gigantic radiator (Zalman have a product for that too, though not for really hot systems), which'd probably be OK for passive cooling, or a small radiator with fan on the end of a lot of tubing that you could put far, far away. But then you'd need a more powerful pump, which might break your noise budget by itself.

Or you could just connect a cold tap to the input of your water cooling rig and let the warm exhaust water dribble into the drain or somewhere, but then environmentalists would beat you to death with naturally fallen, non-truck-transported sticks.

So truly fanless x86-compatible computing is difficult, if not impossible, to achieve. Better to settle for low noise computing, where your PC makes no more racket than, say, a gentle breeze in the trees outside. That's much easier.

Back in the day when CPUs didn't even need fans on them, a single weedy fan in the power supply was more than good enough to haul air through any desktop or tower machine that wasn't packed full of disk drives. Even after everything got crusted up with dust, even if the back of the case was quite hard up against the wall, even if you put the thing on shag pile carpet, it'd be OK. Those old beige-box PSU fans were generally pretty quiet, and could be made quieter still if you swapped them out for a lower power unit (PSU fans are always 12V DC units, usually 80mm), and added a similarly quiet intake fan at the front of the case to take up the slack.

Today, you need more throughflow, but most cases are designed with this in mind - all kinds of cheap cases at least have mounting locations for multiple fans, and may come with them as standard equipment. If you make those fans low powered and, preferably, big (a 120mm fan can move around twice as much air as an 80mm unit, for the same noise and power budget), and you're vigilant about dust clogs, you can easily keep even a quite tweaky machine quiet and cool, as long as your ambient temperature isn't too outrageous.

So where do "silent" PSUs fit into all this?

http://dansdata.com/phantom500.htm

__________________
lazyman

Opteron 165 (2) @2.85 1.42 vcore AMD Stock HSF + Chill Vent II

Sidney

Without the birds singing living in the country; or without diesel bus driving by every 10 minutes, ambulance and cop car sirens living in the city

Then, people paid a lot of money for a computer; only older people could afford them and they could not hear well.

__________________
lazyman

Opteron 165 (2) @2.85 1.42 vcore AMD Stock HSF + Chill Vent II