>And I still would like to know which chips specify 3V dropout
>though.  If you have any clues, please let me know.

I have a feeling that this 3V has become a "rule of thumb" when using 78xx
regulators, on the basis that the data sheet gave around 2.5V. This then
meant there is a bit of headroom for ripple etc.

Then there is the other problem about the way you are going about things. It
seems to me that you are pushing the dropout spec of the 7812, and as a
result may run into strife later. However your load is "only" fans, so it is
not actually affecting you if the output does actually drop out of
regulation. But then again I suspect you may be able to run the fans without
the regulator at all :))

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