Some time ago an old K6-II 500 system came into my possession. It has the most horribly low-quality motherboard (made by PC Chips), and is slow enough that you need to take up a hobby to fill the time spent waiting for it to do stuff, but nonetheless it has served many people well over the years and I wanted it to continue to do so. Therefore I have turned it into a file server, a purpose for which its low power consumption is ideal and its low performance not a hindrance.
The CPU heatsink was tiny and the fan worn out. As a replacement, a relatively enormous socket-A heatsink just about fits, complemented by one of a pair of green LED fans that I had to buy because they were only Â£1 each. With the fan at 5V it is inaudible when the case side is on. The other fan went into the PSU, also undervolted to 5V.
Two 120GB hard drives provide minimal storage space for the moment. Larger drives will be fitted as available. They are suspended by bicycle inner tubes which do an admirable job of absorbing hum, and with AAM turned right up the drives are barely audible even from very close by. There is provision for a third drive under the current two. The optical drive is disconnected to save power.
There's very little else inside the case because what little hardware is needed for a file server is all integrated into the motherboard: Graphics (not really needed since everything can be managed remotely, but one must be present for things to work), network and USB.
In the top two drive bays you can see das blinkenlights that allow useful information like network utilization to be read at a glance. The green LED fans cast a pleasing glow through the holes in the panels. There's a 3.5" drive bay blanking plate missing because there used to be a floppy drive in there and spare blanking plates are strangely impossible to purchase.
The system draws 30W from the mains when idle, going up to about 50W under load, plus a few more watts for each hard drive that's active. That's with the CPU at 500MHz and undervolted to 2.0V (the lowest setting the BIOS allows) and the ancient PSU which is likely to be of low efficiency. It's just about audible from close by during quiet periods, but totally undetectable if there's any ambient noise like cars or birds. The CPU temperature is unfortunately not readable by any software I can find, but the heatsink remains cold to the touch. The hard drives reach about 35C in a room of 22C.