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From: yarvin-norman@cs.yale.edu (Norman Yarvin)
Newsgroups: comp.sys.att
Subject: Re: What is the best fan configuration for a 3B1
Message-ID: <25738@cs.yale.edu>
Date: 6 Aug 90 00:59:33 GMT
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In article <993@galaxia.Newport.RI.US> dave@galaxia.Newport.RI.US writes:
>I have a 7300/3b1 and am trying to determine what the best possible fan
>configuration is to keep the thing cooled.
>
>The possible fan configurations that I have come up with are as follows:
>
>	- two fans blowing out (default config for 7300)
>	- one fan blowing out (default for 3b1??)

The default for the 3b1 is indeed a single fan on the power supply side.
Supposedly a normal machine is best cooled by one fan only; for your
double-hard-drive machine two fans might be better.  I have run my machine
with two fans and with one; with two fans most of the heat exits out the
power supply side anyway.

>I am currently running with one fan blowing in (at the power supply) and
>one fan blowing out and it seems to be keeping the machine fairly cool.

The power supply is a large (the main?) source of heat in the computer.
Your configuration blows air directly over the power supply, cooling it, but
then that hot air is forced through the rest of the computer.  Also, with
fans blowing out, air is drawn through the lower part of the computer; if
the upper part of the computer has one fan blowing in and one blowing out,
there is presumably less of this.

Inward-pointing fans also have the disadvantage that they dissipate the heat
produced by the fan into the computer.

Also, a one-inward, one-outward scheme will push about one fan's worth of
air through the computer.  (It will blow a bit more than one fan's worth,
because two fans halves the drag per fan.)

>  Would it be better to have the
>intake fan on the side away from the power supply?

Probably the best way of increasing cooling is to replace the fans with
higher-volume ones.  I have done this, and the air out of my computer is
significantly cooler.  Higher-volume fans make more noise, though.

--
Norman Yarvin					yarvin-norman@cs.yale.edu