Fan reversal on 3b1/7300

[Bill Mayhew]

The air flow of the 3b1's fan can be easily reversed by simply
turning the fan end-over-end in its holder.  There are a couple of
disadvantages to using positive pressure cooling though.  Namely,
all the air is first blown across the power supply, thus sending a
wave of heated air over the rest of the components.  Positive
pressure tends to have less even air flow inside the machine, thus
causing hot spots.  Adding a second fan per the original AT&T
specifications when reversing the air flow direction would probably
be a good idea.

I think I'd stick with the original cooling scheme and just make a
point of it to vacuum the inscence and stir-fried-animal-part dust
out of the machine every six months or so.

--Bill