It occurred to me that Andy Ruhl wrote in gmane.os.netbsd.ports.i386:
> I also have another board with a slot 1 CPU mount, but I have the
> socket 370 converter for it. If there was a fanless CPU for slot 1,
> that might work as well.

Well, I have a P3 @ 733 MHz which is operated fanless - but only just. The
CPU is located just next to the power supply, which is designed to suck
in air instead of blow it out. On top of that, Compaq designed it such way
that the CPU temperature regulates the speed of the power supply fan, so
it's a bit cheating.

Other than that, a modern Socket A CPU cooler *will* fit on a socket 370
socket - provided there's enough space. Modern coolers tend to be a bit
oversized, so nearby capacitors might spoil the fun.