Hello,

I've noticed that a lot of the "case modder" types are using the +5 and
+12 volts from their computer switching power supplies as 7 volts (12 to
5) to drive their 12 volt fans at lower than normal speeds.

A question came up in a conversation on IRC the other day, about the
safety of this practice.

I located a schematic of a "typical" ATX power supply here:
http://www.acs.comcen.com.au/atxps.html

It appears there are diodes in series with the outputs, so as far as I
can tell, the current must be flowing through other loads on the +5
rail, and thus this technique is dependant on having a (heavily) loaded
+5 rail to prevent pushing the +5 out of regulation.

Is this hypothesis correct?  Are there potentially bad effects even if
the +5 rail is heavily loaded?

-Jason

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