Going to one HD 4543

Then why does Intel suggest blowing cool air horizontally over the heat sinks? Blowing down (allowing air to leak out at the sides, with the air leaking forward opposing the prevailing airflow in the case), or blowing up, sucking in air from the sides (also opposing the prevailing airflow in the case) are both inefficient.

Hot air does not cool as well as cold air. I do not understand what measure power supply with two fans (in series) that are temperature controlled, so the fans turn slowly if the power supply is relatively cool inside, and turn fast when the power supply is warm inside. They point outwards, as is usual. If you reverse the fans and it is cool outside, the fans would turn slowly and push the hot exhaust over the processor(s). If it is warm outside, the fans would turn faster and push even hotter exhaust over the processors. This seems crazy to me. But is it cool enough?

Not the compromise of running hot air over the processor. If it is a typical machine, cool air enters from the front, pbuttes over the processor (heating the air some) and then through the power supply (heating it much more) and then exhausted outside at the back of the box.

In my machine, the box is pressurized by 5 intake fans (three for the bottom of the tower, two for the top) and 5 exhaust fans (the two in series in the power supply, three in the top (4 in the top are mainly to cool the 4 10,000rpm Ultra-320 SCSI hard drives, but the CD-ROM drive and the tape drive are up there too), and a 90mm fan at the rear of the bottom compartment. The upper compartment is has several large apertures for cables and air to move from the bottom to the top.

Each processor has a fan whose intake is very near the front of the box and they pick up cool air from the processor, blow it through processor wind tunnels over the processor heat sinks, and direct it to the rear where most of it is exhausted by the 90mm fan at the rear, and some goes to the top.

Here is how Intel think cooling should be managed.

ftp:--download.intel.com-design-Xeon-guides-29834803.pdf

But then get a slower processor that will put out less heat to begin with.

If the object is quietness over reliability, why bother with fans at all? It is really important to adequately cool processors because if they go over temperature they will get flakey and not recover completely on cooling. What difference does it make if it is quiet then?

-- .~. Jean-David Beyer Registered Linux User 85642. V PGP-Key: 9A2FC99A Registered Machine 241939. ^^-^^ 07:50:00 up 71 days, 1:45, 3 users, load average: 4.26, 4.25, 4.14